The Companion Auto Update plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘update_delay_days’ parameter in all versions up to, and including, 3.9.2 due insufficient input sanitization output escaping. This makes it possible authenticated attackers, with administrator-level access, inject arbitrary web scripts pages that will execute whenever a user accesses an injected page. only affects multi-site installations where unfiltered_html has been disabled.