MonsterInsights Pro Plugin up to 10.x class-system-check.php backdoor

Summaryinfo

A vulnerability was found in MonsterInsights Pro Plugin up to 10.x. It has been rated as problematic. Affected is an unknown function of the file class-system-check.php. Performing a manipulation results in backdoor. This vulnerability is known as CVE-2026-11976. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as problematic, was found in MonsterInsights Pro Plugin up to 10.x. This affects an unknown function of the file class-system-check.php. The manipulation with an unknown input leads to a backdoor vulnerability. CWE is classifying the issue as CWE-912. The product contains functionality that is not documented, not part of the specification, and not accessible through an interface or command sequence that is obvious to the product's users or administrators. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

The official MonsterInsights Pro update distribution bucket (`monster-insights.s3.amazonaws.com`) was compromised. Both the current release (10.2.2) and the version MonsterInsights rolled back to (10.2.0) contain a malicious file, `class-system-check.php`. Three distinct variants were observed on 2026-06-11, all sharing the same AES-256-GCM key, confirming a single threat actor. The attacker retains write access to the S3 bucket and has been actively iterating on the payload throughout the day.

It is possible to read the advisory at wpscan.com. This vulnerability is uniquely identified as CVE-2026-11976 since 06/11/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. The exploitation requires an enhanced level of successful authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1588.001 according to MITRE ATT&CK.

By approaching the search of inurl:class-system-check.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 11.0.0 eliminates this vulnerability.

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Productinfo

Vendor

• MonsterInsights

Name

• Pro Plugin

Version

• 10.x

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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