What the vulnerability does
01Description
The User Profile Builder plugin for WordPress is vulnerable to Authentication Bypass via Type Confusion in versions up to, and including, 3.16.4. This is due to the wppb_log_in_user() function calling absint() on the return value of wp_insert_user() before performing an is_wp_error() check — when a registration is submitted with a 61–70 character username, WordPress core rejects it with a WP_Error object, but absint() coerces that object to the integer 1 before the error check can short-circuit execution, causing the plugin to bind and return a transient-backed autologin nonce tied to user ID 1. This makes it possible for unauthenticated attackers to log in as the site's Administrator account (user ID 1), resulting in full administrative takeover of the site.
Explanation of Vulnerability in Simple Terms
02Summary
User Profile Builder versions up to 3.16.4 contain a type conversion flaw that allows unauthenticated attackers to read and modify sensitive data or run their own code on the site. The vulnerability requires no user interaction and can be exploited over the network. Site administrators should update immediately to a version newer than 3.16.4.
What an attacker can do
03Attacker Capabilities
Read sensitive data, modify site content, or run their own code on the site without authentication.
Potential impact on your site
04Site Impact
Complete compromise of the site: data theft, content manipulation, and malware installation are all possible.
Conditions required to exploit
05Prerequisites
None. The attacker needs only network access; no login or user interaction required.
Key dates
06Disclosure timeline
August 15, 2026
CVE published
