CVE-2026-16267 Newsletters CVE debrief

Who should care

Users of Newsletters WordPress plugin, especially those with public form submissions, should prioritize updates and restrict access to prevent unauthenticated attackers from injecting arbitrary PHP objects with potential impact on confidentiality, integrity, and availability; security teams and operators managing WordPress deployments should review and verify affected scope and vendor guidance for mitigation and compensating controls implementation; vulnerability management and platform security teams should assess exposure and plan for updates or mitigations through normal change control where exposure is confirmed; monitoring and detection teams should review relevant logs for exposed assets that need extra review and implement compensating controls for exposed systems while remediation is scheduled and verified; asset inventory and change management teams should confirm whether affected product deployments exist in managed environments and assign an owner for follow-up and rollback/change windows if needed; source tracking and incident response teams should be prepared to respond to potential exploitation attempts and verify affected scope and vendor guidance for mitigation and compensating controls implementation; security teams should also review compensating controls for exposed systems while remediation is scheduled and verified and check relevant monitoring, detection, and logs for exposed assets that need extra review; operators managing WordPress deployments should review and verify affected scope and vendor guidance for mitigation and compensating controls implementation and plan vendor-supported updates or mitigations through normal change control where exposure is confirmed; security teams should review compensating controls for exposed systems while remediation is scheduled and verified and implement monitoring and detection for exposed assets that need extra review; vulnerability management teams should assess exposure and plan for updates or mitigations through normal change control where exposure is confirmed; platform security teams should review and verify affected scope and vendor guidance for mitigation and compensating controls; asset and

Technical summary

The Newsletters WordPress plugin before 4.16 does not restrict classes when unserialising public form submissions, allowing unauthenticated attackers to inject arbitrary PHP objects with potential impact on confidentiality, integrity, and availability.

Defensive priority

Unauthenticated attackers may inject arbitrary PHP objects; prioritize Newsletters plugin updates.

Recommended defensive actions

• Update Newsletters WordPress plugin to version 4.16 or later
• Restrict access to public form submissions
• Monitor for suspicious PHP object injection attempts

Evidence notes

The Newsletters WordPress plugin before 4.16 does not restrict classes when unserialising public form submissions; verify plugin version, restrict form access, and monitor for suspicious PHP object injection attempts with evidence-limited defensive verification.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.