CVE-2012-6453

Step 1: Payload Delivery: The attacker crafts a malicious RSS feed containing JavaScript code within the feed's content (e.g., in the title, description, or other fields). This JavaScript is designed to perform actions like stealing cookies, redirecting the user, or defacing the website.

Step 2: Feed Ingestion: The attacker tricks a user into subscribing to or viewing the malicious RSS feed within the vulnerable MediaWiki instance using the RSS Reader extension.

Step 3: Vulnerability Trigger: The RSS Reader extension processes the malicious feed, but fails to properly sanitize or escape the JavaScript code within the feed's content.

Step 4: Code Execution: When the MediaWiki page renders the RSS feed content, the attacker's JavaScript code is executed within the user's browser, as part of the MediaWiki page. This allows the attacker to execute arbitrary code in the context of the user's session.

The vulnerability stems from insufficient input validation and output encoding within the RSS Reader extension. Specifically, the extension fails to properly sanitize or escape user-supplied data from RSS feed entries before rendering it on the MediaWiki page. This allows attackers to inject malicious JavaScript code within the RSS feed's content, which is then executed by the victim's browser when the feed is displayed. The root cause is a lack of proper HTML encoding or JavaScript escaping of the RSS feed data before it is inserted into the HTML output. This allows the attacker to craft an RSS feed containing malicious JavaScript, which is then executed in the context of the user's browser, leading to XSS.