CVE-2026-86813: Unknown Metform

Medium severity, CVSS 4.8. EPSS: 0.2% chance of exploitation in the next 30 days.

The MetForm WordPress plugin before 4.1.9 does not properly neutralize newline characters in user-submitted values that are placed into notification email headers, allowing unauthenticated attackers to inject additional email headers, such as Bcc, into the emails the site sends when a submitted field value is configured to populate a header.

Affected products

• Unknown Metform: before 4.1.9 (fixed in 4.1.9)

Published 2026-09-11. Last modified 2026-09-11.