How do Web Applications get attacked?

how do web applications get attacked

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With the widespread use of smartphones, the Internet of Things [IoT] & cloud computing, web applications have become the primary means of delivering services & content to users. However, as the reliance on web applications grows, so does the need for robust security measures to protect these applications from various threats. Robust security measures are imperative to safeguard web applications from an increasingly sophisticated range of cyber threats.

With the vast amounts of sensitive data handled by web applications, including personal & financial information, a breach can have severe consequences. Implementing strong security measures ensures the Confidentiality, Integrity & Availability [CIA] of web applications, fostering user trust & protecting against potential data breaches, financial losses, reputation damage & legal liabilities. Understanding how web applications can be attacked is crucial for developers, administrators & users to ensure the safety & integrity of sensitive information.

Anatomy of a Web Application

Before diving into the world of web application security, it is essential to understand the components & layers that make up a typical web application architecture. A web application consists of client-side & server-side components, which interact with each other through various communication protocols such as HTTP & HTTPS. 

Exploring the anatomy of a web application lays the foundation for comprehending the vulnerabilities that can be exploited. Here is an explanation of the key components & layers:

  1. Client-Side Components:
    1. User Interface [UI]: The UI layer is responsible for presenting the web application to the user. It includes elements such as HTML, CSS & JavaScript that render the visual & interactive aspects of the application in the user’s web browser.
    2. User Input Handling: This component manages the user’s interactions with the application, capturing input through forms, buttons & other user interface elements.
  2. Server-Side Components:
    1. Web Server: The web server handles incoming requests from clients & delivers responses. It typically runs server-side scripts or applications & communicates with other components in the backend.
    2. Application Server: The application server hosts the core logic & functionality of the web application. It processes the user requests, interacts with databases & executes business logic.
    3. Database: The database stores & manages the persistent data used by the web application. It can be a Relational Database Management System [RDBMS] like MySQL or PostgreSQL or a NoSQL database like MongoDB.
  3. Communication Protocols:
    1. Hypertext Transfer Protocol [HTTP]: HTTP is the foundation of communication between web browsers & servers. It enables the exchange of requests & responses, allowing users to access web applications over the internet.
    2. Secure HTTP [HTTPS]: HTTPS is an extension of HTTP that adds encryption & secure authentication. It ensures the confidentiality & integrity of data transmitted between the client & the server, providing protection against eavesdropping & tampering.
  4. Additional Layers:
    1. Middleware: Middleware components act as intermediaries between the web server & the application server, providing additional functionalities such as authentication, caching, session management & routing.
    2. Security Layer: This layer includes security mechanisms, such as Firewalls, Intrusion Detection Systems [IDS] & Access Controls, to protect the web application from malicious activities & unauthorised access.
    3. Integration Layer: The integration layer enables the web application to communicate with external systems, services or APIs, allowing data exchange & integration with third-party functionalities.

These components & layers work in unison to facilitate the flow of data & requests, process business logic & deliver a seamless user experience in a web application.

Common Web Application Vulnerabilities

Web Application Vulnerabilities refers to a flaw or weakness in the design, implementation or configuration of a web application that can be exploited by attackers. These vulnerabilities may allow unauthorised access, data manipulation, injection attacks, cross-site scripting or other malicious activities that compromise the security & integrity of the application & its users’ data. Some of the common web application vulnerabilities are:

  1. SQL Injection: SQL Injection is a common web application vulnerability where attackers exploit improper handling of user-supplied input in SQL queries. By inserting malicious SQL code into input fields, attackers can manipulate the query’s logic, potentially bypassing authentication, extracting sensitive data or modifying the database. The impact of a successful SQL injection attack can be severe, including unauthorised access to databases, data breaches, financial loss, compromised user accounts & damage to an organisation’s reputation. Preventing SQL injection involves using parameterized queries or prepared statements, input validation & sanitization, strict access controls & keeping database software & frameworks up to date with security patches. Regular security testing & code reviews are also crucial for mitigating this vulnerability.
  2. Cross-Site Scripting [XSS]: Cross-Site Scripting [XSS] is a web application vulnerability where attackers inject malicious scripts into web pages viewed by other users. XSS vulnerabilities arise when user-supplied input is not properly validated or sanitised before being displayed on a website. Attackers exploit this by injecting scripts that can steal sensitive user information, hijack user sessions or deface websites. There are three main types of XSS attacks: Stored XSS (persistent), Reflected XSS (non-persistent) & DOM-based XSS. To mitigate XSS vulnerabilities, developers should implement input validation & output encoding, utilise security libraries & frameworks, enforce strict Content Security Policies [CSP] & regularly patch & update web application components. User awareness & education about safe browsing habits are also essential.
  3. Cross-Site Request Forgery [CSRF]: Cross-Site Request Forgery [CSRF] is an attack where an attacker tricks a victim into unknowingly executing unauthorised actions on a trusted website. It bypasses the user’s trust in the website by exploiting the fact that the website assumes the requests originate from the user. For example, an attacker could embed a malicious link or script in an email or website, causing the victim’s browser to execute requests on their behalf. This can lead to actions like changing passwords, making unauthorised transactions or altering account settings. To prevent CSRF attacks, developers should implement measures such as using anti-CSRF tokens, checking the Referer header, employing SameSite cookies & implementing CAPTCHAs for critical actions. Additionally, user education & awareness about potential CSRF risks are crucial.
  4. Cross-Site Script Inclusion [XSSI]: Cross-Site Script Inclusion [XSSI] vulnerabilities occur when an attacker includes an external script from a malicious domain into a trusted website, bypassing the browser’s same-origin policy. This can lead to various implications such as unauthorised access to sensitive data, session hijacking or injection of malicious code. Attackers exploit XSSI vulnerabilities by leveraging the ability to include external scripts, cookies or other resources from their own domains. To secure against XSSI attacks, developers should validate & sanitise input, utilise Content Security Policy [CSP] to restrict script inclusion, implement proper server-side access controls & use Subresource Integrity [SRI] to ensure script integrity. Regular security assessments & staying updated on emerging XSSI attack techniques are also recommended.
  5. Security Misconfigurations: Security misconfigurations refer to improper or inadequate configuration of security settings in web applications, leaving them vulnerable to attacks. Common misconfigurations include default settings, weak passwords, open permissions, outdated software or exposed sensitive information. These misconfigurations can lead to unauthorised access, data breaches, system compromise or the exploitation of vulnerabilities. To avoid security misconfigurations, developers should follow best practices such as securely configuring servers & frameworks, removing default accounts & configurations, applying the principle of least privilege, regularly updating software & patches, conducting security assessments, implementing secure network configurations & employing strong password policies. Regular monitoring & auditing of configurations are also essential.
  6. Broken Authentication & Session Management: Broken Authentication & Session Management vulnerabilities pose significant risks to the security of web applications. Strong authentication mechanisms, such as secure password policies, Multi-Factor Authentication [MFA] & secure session management, are crucial to prevent unauthorised access to user accounts. Common vulnerabilities include weak passwords, session fixation, session hijacking or inadequate session expiration. To enhance authentication & session security, developers should enforce secure password policies, implement session management best practices, such as random session IDs, session expiration & secure session storage. Additionally, incorporating secure protocols like HTTPS, employing secure session handling libraries & regularly auditing & monitoring authentication & session management mechanisms can help mitigate these vulnerabilities.
  7. Denial-of-Service [DoS] Attacks: Denial-of-Service [DoS] attacks aim to disrupt or disable web applications by overwhelming them with excessive traffic or exploiting vulnerabilities in their infrastructure. These attacks can have a severe impact, causing service unavailability, slowdowns or crashes, leading to financial losses, reputation damage & customer dissatisfaction. Different types of DoS attacks include flood attacks (e.g., TCP/IP, HTTP floods) that overload network or server resources & amplification attacks that leverage vulnerable systems to generate massive traffic. Mitigating DoS attacks involves implementing measures like rate limiting, traffic filtering, load balancing, deploying Intrusion Detection & Prevention Systems [IDPS], using Content Delivery Networks [CDNs] & employing robust network infrastructure. Regular monitoring & incident response planning are also essential.

Advanced Web Application Attacks

Building upon the knowledge gained from the previous section, this section delves into advanced web application attacks. Advanced web application attacks push the boundaries of exploitation techniques & require a deep understanding of web application vulnerabilities. From advanced forms of Cross-Site Scripting [XSS] to Server-Side Request Forgery [SSRF] & Remote Code Execution [RCE], these attacks demand advanced knowledge & countermeasures to protect web applications from sophisticated & potentially devastating breaches.

Cross-Site Scripting [XSS] beyond the basics

Advanced XSS [Cross-Site Scripting] techniques expand upon the basic XSS attacks to exploit web application vulnerabilities more effectively. Polyglot XSS involves crafting payloads that can be interpreted as multiple languages, evading input filters & increasing the chances of successful exploitation. Blind XSS refers to injecting malicious code without direct feedback, often through stored payloads or other covert methods. Stored XSS occurs when the injected scripts are permanently stored on the target website, affecting multiple users. These advanced XSS techniques enable attackers to steal sensitive data, deface websites or spread malware, underscoring the importance of robust mitigation measures & secure coding practices in web application development.

Real-world examples of advanced XSS attacks showcase the severity & potential impact of these vulnerabilities. One notable example is the Samy worm, where a MySpace profile used a combination of XSS & self-propagation techniques to infect over one million users, modifying their profiles & spreading rapidly. Another example is the Apache Jira vulnerability, where an attacker leveraged a blind XSS flaw to execute arbitrary code, compromising the popular issue tracking system. These incidents highlight how advanced XSS attacks can lead to unauthorised access, data theft, defacement & the propagation of malware. Vigilance, secure coding practices & prompt patching are crucial in mitigating these threats.

Countermeasures for advanced XSS attacks involve a combination of preventive & mitigative measures to protect web applications:

  • Input Validation & Output Encoding: Implement strict input validation to filter & sanitise user input. Apply output encoding to ensure that any user-generated content is properly escaped before being displayed.
  • Content Security Policies [CSP]: Use CSP to define a whitelist of trusted sources for scripts, stylesheets & other resources, preventing the execution of untrusted code.
  • Secure Coding Practices: Follow secure coding practices to minimise the risk of XSS vulnerabilities, such as input validation, secure session handling & proper error handling.
  • Web Application Firewalls [WAFs]: Deploy WAFs that can detect & block XSS attacks using pattern matching, heuristics & behavioural analysis.
  • Regular Security Testing: Conduct comprehensive security testing, including vulnerability scanning, penetration testing & code reviews, to identify & remediate XSS vulnerabilities.

Implementing these countermeasures strengthens the security posture of web applications & reduces the risk of falling victim to advanced XSS attacks.

Server-Side Request Forgery [SSRF]

Server-Side Request Forgery [SSRF] vulnerabilities occur when an attacker manipulates a web application to make unauthorised requests from the server to internal or external resources. Exploiting SSRF vulnerabilities involves tricking the server into sending malicious requests, potentially leading to data leakage, remote code execution or accessing sensitive resources. Attackers can abuse SSRF to bypass firewalls, scan internal networks, retrieve sensitive information or launch attacks on other systems. By manipulating input fields or URL parameters, they can control the server’s requests & exploit the trust placed in the server’s identity. Proper input validation, strong access controls & whitelisting trusted resources are essential to prevent SSRF attacks.

Server-Side Request Forgery [SSRF] attacks can have severe consequences, leading to various security breaches & compromises. Examples of SSRF attacks include:

  • Accessing internal resources: Attackers can exploit SSRF to access sensitive internal resources such as databases, files or administrative interfaces, bypassing network boundaries & firewalls.
  • Service scanning: By sending requests to internal services or ports, attackers can perform service discovery, identifying vulnerable systems or potential entry points for further attacks.
  • Remote code execution: SSRF can be leveraged to execute arbitrary code on the server, leading to complete compromise of the application or the underlying infrastructure.
  • Data exfiltration: Attackers can extract sensitive data from internal systems by making requests to external servers & manipulating the responses.

The impact of SSRF attacks can range from unauthorised access to sensitive information, system compromise, data breaches, financial loss, reputational damage & legal liabilities. It highlights the importance of implementing strong security measures to prevent & mitigate such attacks. 

Preventing Server-Side Request Forgery [SSRF] attacks requires implementing robust security measures. Here are some best practices to mitigate the risk:

  • Input validation & filtering: Implement strict input validation & sanitization to ensure that user-supplied URLs or input cannot be manipulated to make unauthorised requests.
  • Whitelisting trusted resources: Maintain a whitelist of trusted domains & resources that the server is allowed to access & ensure that requests are limited to these trusted sources.
  • Use of network-level protections: Employ network-level protections such as firewalls, network segmentation & access controls to prevent unauthorised requests from reaching internal resources.
  • Limiting request destinations: Configure the server to only allow requests to specific IP addresses, hostnames or designated endpoints, rather than accepting arbitrary URLs.
  • Reducing server-side trust: Minimise the trust placed in user-provided URLs or input by implementing least privilege principles & validating requests against a set of defined rules.

By following these best practices, organisations can strengthen their defences against SSRF attacks & minimise the risk of unauthorised access to internal resources. 

Remote Code Execution [RCE]

Remote Code Execution [RCE] vulnerabilities pose significant threats to web applications & their underlying systems. These vulnerabilities allow attackers to execute arbitrary code remotely, giving them control over the application or server. The consequences of RCE can be severe, including complete system compromise, unauthorised access to sensitive data, modification or deletion of files & even launching further attacks within the network. Attackers can exploit RCE vulnerabilities to gain persistent access, propagate malware or perform other malicious activities. Understanding the gravity of RCE vulnerabilities highlights the importance of implementing robust security measures, such as code reviews, secure coding practices, input validation & regular patching, to prevent & mitigate these risks.

Exploiting Remote Code Execution [RCE] vulnerabilities involves various techniques that attackers employ to execute arbitrary code on a target system. Common techniques include:

  • Code injection: Attackers inject malicious code, often through user input or unvalidated data, that gets executed by the application or server.
  • Command injection: By injecting malicious commands into user input fields, attackers manipulate the system to execute arbitrary commands, leading to RCE.
  • File inclusion vulnerabilities: Exploiting weaknesses in file inclusion mechanisms, attackers can include malicious files that are executed by the application or server.
  • Deserialization vulnerabilities: Attackers manipulate serialised data to trigger the execution of arbitrary code during the deserialization process.
  • Exploiting software vulnerabilities: RCE can be achieved by exploiting software vulnerabilities, such as buffer overflows, code injection flaws or insecure deserialization.

These techniques highlight the need for robust security practices, including secure coding, input validation, strong access controls & regular patching, to prevent & mitigate the exploitation of RCE vulnerabilities.


In conclusion, we have explored various web application attacks, including SQL injection, XSS, CSRF, XSSI, security misconfigurations, broken authentication, DoS attacks & advanced techniques like advanced XSS, SSRF & RCE. Understanding these attacks helps us better defend against them.

The ever-evolving threat landscape highlights the importance of staying vigilant & proactive in securing web applications. Implementing robust security measures, including input validation, output encoding, secure authentication, session management & regular security testing, is crucial to mitigate the risks. 

It is essential to follow best practices, such as secure coding, patch management & user education, while adopting a comprehensive security approach that combines preventive measures, monitoring & incident response. By prioritising security, we can protect the integrity, confidentiality & availability of web applications in our increasingly interconnected world.


What type of attack against a web application?

One type of attack against a web application is SQL injection, where attackers manipulate input fields to execute malicious SQL commands, potentially compromising the integrity of the application’s database. This can lead to unauthorised data access, data manipulation or even complete control over the database.

What makes web applications a vulnerable point of attack?

Web applications are vulnerable points of attack due to various factors. These include insufficient input validation, insecure coding practices, misconfigurations, outdated software & the potential for attackers to exploit vulnerabilities to gain unauthorised access, steal data or execute malicious code on the server or client-side.

What are the 2 threats to web applications?

Two significant threats to web applications are:

  1. Unvalidated input: When web applications do not properly validate or sanitise user input, it can lead to vulnerabilities like SQL injection, XSS or command injection.
  2. Inadequate access controls: Insufficient access controls allow unauthorised users to access restricted areas or perform actions they shouldn’t, potentially leading to data breaches or unauthorised system manipulation. 
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