wpForo Forum < 3.1.7 - Authenticated (Subscriber+) Stored Cross-Site Scripting via 'telegram' Profile Field

Description

The wpForo Forum plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'telegram' profile field in versions up to, and including, 3.1.6. This is due to insufficient input sanitization and output escaping in the profile_update action — the raw $_POST['data'] array is copied into a $custom_fields variable before validate() and sanitize() run, both of which operate only on a parallel $user reference, leaving $custom_fields unsanitized when it is persisted via update_custom_fields(); on render, wpforo_decode() reverses the entity encoding and the value is echoed without escaping in field_wrap_profile(). This makes it possible for authenticated attackers, with subscriber-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.