Output validation vulnerability in Advanced Custom Fields (ACF) 5.7.11

Advanced Custom Fields is a plugin for WordPress, a web-based content management system. There was a vulnerability in versions of Advanced Custom Fields before 5.7.12 that could potentially allow a malicious user to execute code on a website using Advanced Custom Fields. The vulnerability was caused by a failure to properly sanitize user input before it was passed to the unserialize() function. This could allow a malicious user with a low level of access to execute code on the website if a usable gadget was present in a theme or plugin installed on the same website.