Description
In MediaWiki before 1.31.10 and 1.32.x through 1.34.x before 1.34.4, XSS related to jQuery can occur. The attacker creates a message with [javascript:payload xss] and turns it into a jQuery object with mw.message().parse(). The expected result is that the jQuery object does not contain an <a> tag (or it does not have a href attribute, or it's empty, etc.). The actual result is that the object contains an <a href ="javascript... that executes when clicked.
Remediation
References
Related Vulnerabilities
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Jenkins Permissions, Privileges, and Access Controls Vulnerability (CVE-2015-1810)
Joomla Permissions, Privileges, and Access Controls Vulnerability (CVE-2006-0114)
WordPress 4.5.x Arbitrary File Deletion Vulnerability (4.5 - 4.5.14)