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Vulnerability · Published Aug 15, 2026 · Assigned by Wordfence

CVE-2026-15826User Profile Builder <= 3.16.4 - Unauthenticated Authentication Bypass via Type Confusion to Administrator Account Takeover via 'username' Parameter

Critical 9.8

In plain English

A critical-severity security flaw in User Profile Builder – Beautiful User Registration Forms, User Profiles & User Role Editor from cozmoslabs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 3.9% (higher than 90% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei, public proof-of-concept code.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)3.9%top 9.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack tooling2Nuclei, Public PoC

Official description

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.

Affected products (as reported)

VendorProductVersions
cozmoslabs User Profile Builder – Beautiful User Registration Forms, User Profiles & User Role Editor 0 – through 3.16.4

Weakness: CWE-704 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References