The FV Player 8 plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'fv_player_videos' parameter in all versions up to, and including, 8.1.9 due to insufficient input sanitization and output escaping. 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. This requires the administrator-controlled "Allow visitors to upload videos to their profile" setting to be enabled, without which the vulnerable save routine is inaccessible to Subscriber-level users.