CVE-2023-36675 in MediaWiki
Summary
by MITRE • 06/26/2023
An issue was discovered in MediaWiki before 1.35.11, 1.36.x through 1.38.x before 1.38.7, 1.39.x before 1.39.4, and 1.40.x before 1.40.1. BlockLogFormatter.php in BlockLogFormatter allows XSS in the partial blocks feature.
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Analysis
by VulDB Data Team • 01/15/2026
The vulnerability identified as CVE-2023-36675 represents a cross-site scripting flaw within the MediaWiki platform that affects multiple version ranges including 1.35.11, 1.36.x through 1.38.7, 1.39.x through 1.39.4, and 1.40.x through 1.40.1. This issue specifically resides in the BlockLogFormatter.php component which handles the formatting of block log entries, particularly impacting the partial blocks functionality. The flaw enables attackers to inject malicious scripts into log entries that are subsequently executed in the context of other users' browsers when they view these log entries. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a critical security weakness in web applications where user-provided data is not properly sanitized before being rendered in web pages. The attack vector leverages the partial blocks feature which allows administrators to apply restrictions to specific actions or namespaces rather than complete user blocking, making this particularly dangerous in environments where extensive logging and monitoring occurs.
The technical implementation of this vulnerability occurs when the BlockLogFormatter.php component fails to adequately sanitize user input or log data containing block information before rendering it in HTML format. When partial blocks are created, the system stores information about the restrictions applied to users, and this data is later formatted and displayed in log entries. If an attacker can manipulate or inject malicious content into these log entries, particularly through the partial block configuration parameters, the system's failure to properly escape or filter the content allows JavaScript code to be executed in the browsers of users who view these logs. This type of vulnerability is particularly concerning because it can be exploited by attackers who gain access to write permissions on the MediaWiki instance, or through other means that allow them to inject malicious data into the system's logging mechanism. The exploitation typically requires the attacker to have some level of access to create or modify content that gets logged, which could include the ability to create pages or modify user accounts with partial blocking capabilities.
The operational impact of this vulnerability extends beyond simple script execution, as it can lead to unauthorized access to user sessions, data theft, or further exploitation of the MediaWiki platform. Attackers could potentially steal session cookies, redirect users to malicious websites, or execute commands on behalf of authenticated users who view the compromised log entries. This becomes particularly dangerous in collaborative environments where multiple administrators and users frequently access log information to monitor system activity. The vulnerability can be leveraged to perform session hijacking attacks, where an attacker steals a user's authentication session and gains unauthorized access to their privileges within the MediaWiki system. Additionally, the attack could be used to deface the wiki interface, modify content, or create backdoors for persistent access. The exposure of this vulnerability in multiple version ranges indicates a persistent flaw in the sanitization process that affects MediaWiki installations across different major releases, making it a widespread concern for organizations relying on these platforms for documentation, collaboration, and knowledge management.
Organizations should immediately upgrade to the patched versions of MediaWiki to address this vulnerability, specifically targeting the releases that include fixes for versions 1.35.11, 1.38.7, 1.39.4, and 1.40.1. The mitigation strategy should include implementing proper input validation and output encoding for all user-generated content that appears in log files or administrative interfaces. Security measures should be enhanced to ensure that only authorized personnel have the capability to create partial blocks, and additional logging should be implemented to monitor for suspicious activity in log entries. Network monitoring tools should be configured to detect potential XSS payloads in web traffic, and regular security audits should verify that all user input is properly sanitized before being processed or displayed. The vulnerability also highlights the importance of following secure coding practices as outlined in the OWASP Top 10, specifically addressing the prevention of XSS vulnerabilities through proper input validation and output encoding. Organizations should also consider implementing Content Security Policy headers to add an additional layer of protection against script execution in the browser context, and establish incident response procedures to quickly address potential exploitation attempts. The ATT&CK framework categorizes this type of vulnerability under T1211 - Exploitation for Privilege Escalation and T1566 - Phishing, as attackers could use the XSS to gain elevated privileges or redirect users to malicious sites, making comprehensive security measures essential for protecting MediaWiki installations from exploitation.