The Advanced Custom Fields: Font Awesome plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to and including 5.0.2. This is due to insufficient input validation of JSON field values and unsafe client-side HTML construction in the update_preview() JavaScript function. 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.