CVE-2011-1587 in MediaWiki
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in MediaWiki before 1.16.4, when Internet Explorer 6 or earlier is used, allows remote attackers to inject arbitrary web script or HTML via an uploaded file accessed with a dangerous extension such as .html located before a ? (question mark) in a query string, in conjunction with a modified URI path that has a %2E sequence in place of the . (dot) character. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-1578.
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Analysis
by VulDB Data Team • 11/05/2021
This cross-site scripting vulnerability in MediaWiki affects versions prior to 1.16.4 and specifically targets users operating Internet Explorer 6 or earlier browsers. The flaw represents a sophisticated attack vector that exploits the interaction between file extension handling and URI parsing mechanisms within the MediaWiki platform. The vulnerability stems from an incomplete remediation of CVE-2011-1578, demonstrating how security fixes can sometimes create new attack surfaces when not thoroughly implemented. Attackers can leverage this weakness by uploading files with dangerous extensions such as .html and accessing them through carefully crafted query strings that contain a question mark character, combined with modified URI paths where dots are replaced with %2E sequences. This technique bypasses traditional file extension validation mechanisms by exploiting how older browsers process encoded characters in URLs.
The technical implementation of this vulnerability relies on the specific behavior of Internet Explorer 6 and earlier versions when processing URL-encoded characters and file extensions. When MediaWiki processes a file request with a query string containing a question mark followed by a modified URI path featuring %2E sequences instead of standard dots, the application fails to properly sanitize or validate the file extension portion of the URL. This parsing inconsistency allows malicious scripts to be executed in the context of a victim's browser session, as the application incorrectly interprets the encoded file extension as a valid HTML file type. The vulnerability is particularly dangerous because it requires no user interaction beyond visiting a maliciously crafted URL, making it a server-side attack vector that can be exploited through various delivery mechanisms including phishing emails, malicious links in forums, or compromised web pages.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, steal sensitive user information, manipulate content displayed on the wiki, or redirect users to malicious websites. The attack requires specific conditions to be met including the use of Internet Explorer 6 or earlier, which limits its immediate impact but does not eliminate the risk entirely given the continued use of legacy browsers in certain environments. Security professionals should note that this vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications. The attack pattern also corresponds to techniques documented in the ATT&CK framework under T1566, which covers social engineering methods that can be used to deliver malicious payloads through web-based attack vectors.
The remediation strategy for this vulnerability requires immediate upgrade to MediaWiki version 1.16.4 or later, which contains the complete fix for the XSS vulnerability. Organizations should also implement additional defensive measures including comprehensive input validation, proper URI sanitization, and strict file extension filtering mechanisms. Security teams should consider implementing web application firewalls to detect and block suspicious URL patterns, particularly those containing %2E sequences in file paths. The vulnerability demonstrates the importance of thorough regression testing when implementing security fixes, as the incomplete solution for CVE-2011-1578 created this new attack surface. Organizations using older MediaWiki versions should also consider implementing additional monitoring and logging mechanisms to detect potential exploitation attempts, as the attack requires specific browser and URL conditions that may be detectable through network traffic analysis. Regular security assessments should include verification that all security patches have been properly applied and that no residual vulnerabilities exist from previous fixes.