WordPress DOM XSS Cross-site Scripting Vulnerability Identified By Netsparker

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8th of May 2015, Netsparker annouced yesterday the discovery of critical security vulnerability contained an HTML file found on many WordPress themes, including WordPress.org hosted websites. As reported by Netsparker the specific HTML file is vulnerable to cross-site scripting attacks and session hijack. WordPress.org has already issued an official annoucement and patch (v4.2.2) and recommends WordPress administrators update their website files and themes.

The Genericons icon font package, which is used in a number of popular themes and plugins, contained an HTML file vulnerable to a cross-site scripting attack. All affected themes and plugins hosted on WordPress.org (including the Twenty Fifteen default theme) have been updated yesterday by the WordPress security team to address this issue by removing this nonessential file. To help protect other Genericons usage, WordPress 4.2.2 proactively scans the wp-content directory for this HTML file and removes it. Reported by Robert Abela of Netsparker.

By exploiting a Cross-site scripting vulnerability the attacker can hijack a logged in user’s session. This means that the malicious hacker can change the logged in user’s password and invalidate the session of the victim while the hacker maintains access. As seen from the XSS example in Netsparker's article, if a web application is vulnerable to cross-site scripting and the administrator’s session is hijacked, the malicious hacker exploiting the vulnerability will have full admin privileges on that web application.