Profile Builder Plugin - Authentication Bypass (CVE-2021-24527)

CVE-2021-24527 is a critical vulnerability in the User Registration & User Profile – Profile Builder WordPress plugin prior to version 3.4.9, allowing any user to reset the admin password and gain unauthorized access due to a flaw in reset key validation. Attackers can exploit this bug to take over WordPress sites without alerting the administrator, as no notification is sent when the password is changed.

CrowdSec has been tracking this vulnerability and its exploits since 24th of September 2025.

Insights from the CrowdSec network reveal that the attackers trying to exploit CVE-2021-24527 are composed of a fairly even mix of opportunistic and targeted actors. Some attackers employ preliminary reconnaissance, while others use indiscriminate scanning. CrowdSec network telemetry also shows that exploitation of CVE-2021-24527 has significantly declined over the past week. Attack volumes are well below the long-term average, suggesting attackers are rapidly losing interest. The vulnerability appears to be falling out of active use across most threat landscapes.

Attackers exploit the password reset functionality by sending crafted requests to endpoints with a ?key=<a> parameter, allowing them to reset passwords for arbitrary users, including administrators, without authentication. This activity typically targets URLs associated with the Profile Builder plugin, such as /wp-content/plugins/profile-builder/ or any path containing ?key=<a>.