Quick answers
- Is CVE-2026-66583 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-66583 being exploited in the wild.
- How severe is CVE-2026-66583?
- Critical severity, with a CVSS score of 9.8, published 20 August 2026.
- Which products and versions are affected?
- WPMU DEV Forminator 1.57.0 and earlier.
- Is there a fix for CVE-2026-66583?
- A patch was published on 2026-08-19: Patch released in version 1.57.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-66583 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-66583?
- Check whether you run WPMU DEV Forminator at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a PHP Object Injection flaw in Forminator versions 1.57.0 and earlier that does not properly validate user input before deserializing PHP objects. An unauthenticated attacker can send a malicious payload via network request to trigger deserialization of arbitrary objects, leading to remote code execution (RCE) on the affected server. No authentication is required and the vulnerability is accessible via the web interface. The vulnerability was patched in version 1.57.1.
Affected products
- WPMU DEV Forminator 1.57.0 and earlier
Timeline
- 2026-08-19: disclosed: Vulnerability published by Patchstack
- 2026-08-19: patched: Patch released in version 1.57.1