Stored Cross-Site Scripting
Overview
Stored Cross-Site Scripting (XSS) is a type of computer security vulnerability typically found in web applications. This vulnerability allows attackers to inject malicious scripts into web pages viewed by other users. A stored XSS vulnerability occurs when the data provided by the attacker is saved by the server, and then permanently displayed on "normal" pages returned to other users in the course of regular browsing, without proper HTML escaping.
Mechanism of Action
Stored XSS attacks involve an attacker injecting a script, often written in JavaScript, that is stored on the target server. When a victim navigates to the affected web page, the stored script is served as part of the web page. The victim's browser executes the script because it assumes the script came from a trusted source. The script can then perform a variety of actions, from stealing the user's cookies to performing actions on their behalf.
Vulnerability and Exploitation
Stored XSS vulnerabilities are particularly dangerous because they directly affect all users who view the affected page and the malicious code is embedded in the actual page, making the attack more difficult to detect. Attackers can exploit these vulnerabilities to steal sensitive data, such as login credentials or personal information, or to perform actions on the user's behalf, potentially leading to unauthorized access or privilege escalation.
Prevention and Mitigation
Preventing stored XSS attacks involves proper handling and sanitization of user input. This can be achieved through a variety of methods, including input validation, output encoding, and use of appropriate HTTP headers. Additionally, implementing a robust Content Security Policy can help prevent the execution of unauthorized scripts.
Impact
The impact of a successful stored XSS attack can be significant. Depending on the nature of the web application and the data it handles, an attacker could potentially gain unauthorized access to sensitive data, perform actions on behalf of users, or even gain full control over the affected web application.