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CVE-2026-15826 – Unauthenticated Administrator Account Takeover – WordPress User Profile Builder (Pr

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Summary

CVE-2026-15826 is a critical authentication bypass vulnerability in the Profile Builder Pro (User Profile Builder) WordPress plugin by Cozmoslabs, affecting all versions up to and including 3.16.4. A type-confusion flaw in the plugin’s login-handling code allows unauthenticated attackers to obtain an autologin session as the site’s Administrator account. The vulnerability carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: the plugin’s wppb_log_in_user() function passes the return value of wp_insert_user() through absint() before calling is_wp_error() to check for registration failures.
  • Trigger condition: submitting a front-end registration request with a username 61–70 characters long causes WordPress core to reject the registration and return a WP_Error object instead of a numeric user ID.
  • absint() coerces that WP_Error object into the integer 1, which the plugin then treats as a valid user ID — user ID 1 is typically the original site Administrator.
  • The plugin proceeds to generate and use an autologin nonce for that coerced ID, authenticating the requester as that user.
  • Attack vector: network, no authentication or user interaction required, executed via a standard front-end registration form submission.
  • Impact: full administrative account takeover, granting confidentiality, integrity, and availability impact consistent with complete site compromise.

Affected software

  • Profile Builder Pro / User Profile Builder (WordPress plugin, Cozmoslabs) — all versions up to and including 3.16.4.

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: upgrade Profile Builder Pro / User Profile Builder to a version newer than 3.16.4 that includes the vendor’s fix to the wppb_log_in_user() validation logic.
  • If patching cannot be applied immediately: disable or restrict access to the plugin’s front-end user registration form, or place a web application firewall rule in front of the registration endpoint to block usernames in the 61–70 character range.
  • After remediation: review WordPress user accounts and administrator activity logs for signs of unauthorized login or account creation predating the patch.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Raw response body: /wp-content/plugins/profile-builder-pro/

References

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1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

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