CVE-2026-11366: MonsterInsights < 11.1.0 - Unauthenticated Measurement Protocol Secret Update via Empty-Key HMAC Bypass
Vulnerability summary
CVE-2026-11366 is a medium (CVSS 5.3) Improper Authentication vulnerability in unknown monsterinsights. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.2% of scored vulnerabilities. 1 public exploit is recorded. Fixed in 11.1.0.
Timeline
- 04-08-2026PublishedVulnerability first disclosed.
- 04-08-2026Last modifiedVulnerability information updated.
Description
The MonsterInsights WordPress plugin before 11.1.0 does not correctly validate the signature on one of its unauthenticated AJAX actions: when the MonsterInsights WordPress plugin before 11.1.0 is not connected to Google Analytics the HMAC signing key is empty, which lets unauthenticated attackers forge a valid signature and overwrite a MonsterInsights WordPress plugin before 11.1.0 configuration value, disrupting the MonsterInsights WordPress plugin before 11.1.0's server-side analytics in Manual GA4 mode.
CVSS metrics
3 scores · 3 sources · 1 version- CVE.orgCNA3.7LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:NDiffers
- NVDNIST3.7LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:NDiffers
EPSS trend
Probability
0.25%
Chance of exploitation in the next 30 days
Percentile
15%
Versus all other CVEs
30-day change
Increase +0.06 pp
From 0.19% on 22-09-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundExploit Reference (wpscan.com)
Maturity: unknown
Weaknesses
CWE · root causeAffected systems
Unknown1 product
- monsterinsights< 11.1.0
Wordpress1 product
- google-analytics-for-wordpress≤ 11.0.0 (fixed in 11.1.0)
2 vendors · 2 products