Stored Cross-Site Scripting (XSS) is a type of security vulnerability that affects web applications. It occurs when an attacker injects malicious scripts into a target website, which are then permanently stored and displayed to other users. This form of XSS attack differs from other types of XSS attacks, namely Reflected XSS and DOM-based XSS, in terms of how the malicious script is delivered and executed.
In Stored XSS attacks, the injected script is permanently stored on the target website's server or database. This means that every time a user visits the affected page, the script is retrieved from the server and executed in their browser. The script can be embedded in various user-generated content, such as comments, forum posts, or user profiles. When other users access the same page, the malicious script is displayed and executed in their browsers as well.
One significant difference between Stored XSS and Reflected XSS is the delivery mechanism. In Reflected XSS attacks, the malicious script is embedded in a URL or a form input, which is then reflected back to the user by the web application. For example, an attacker might craft a URL containing a script that steals the victim's cookies. When the victim clicks on the malicious link, the script is executed in their browser. Unlike Stored XSS, the script is not permanently stored on the target server and is only delivered to users who interact with the malicious URL.
Another variant of XSS, known as DOM-based XSS, differs from Stored XSS in terms of how the script is executed. In DOM-based XSS attacks, the malicious script manipulates the Document Object Model (DOM) of the web page directly, without necessarily involving the server or the database. The script typically modifies the page's structure or content, leading to the execution of the attacker's code. This type of XSS attack is often caused by insecure JavaScript coding practices that allow user input to be directly included in the DOM.
To illustrate the difference between Stored XSS and other types of XSS attacks, consider the following example. Suppose a vulnerable web application allows users to post comments on a blog. If an attacker submits a comment containing a malicious script, such as a script that steals user credentials, the script will be stored on the server. Whenever other users access the blog post with the malicious comment, the script will be executed in their browsers, potentially compromising their accounts. This scenario represents a Stored XSS attack.
Stored XSS is a type of XSS attack where a malicious script is permanently stored on a web application's server or database and executed whenever the affected page is accessed. It differs from Reflected XSS, where the script is reflected back to the user by the web application, and DOM-based XSS, where the script directly manipulates the web page's DOM. Understanding these distinctions is crucial for developers and security professionals to effectively mitigate XSS vulnerabilities in web applications.
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