CVE-2026-35569 apostrophecms CVE debrief

Who should care

Defenders responsible for ApostropheCMS installations, particularly those with authenticated users who could be affected by the vulnerability, should assess exposure and apply the patch.

Why it matters

Defenders should prioritize verifying exposure and applying the patch to prevent exploitation, as this vulnerability allows an attacker to execute arbitrary JavaScript in the browser of authenticated users.

• Execution of arbitrary JavaScript in the browser of authenticated users
• Potential access to sensitive data such as usernames, email addresses, and roles
• Possible leveraged authenticated API requests

Technical summary

ApostropheCMS versions 4.28.0 and prior contain a stored cross-site scripting vulnerability in SEO-related fields (SEO Title and Meta Description). An attacker can inject a payload to break out of the intended HTML context and execute arbitrary JavaScript in the browser of any authenticated user who views the affected page. This vulnerability allows for potential access to sensitive data such as usernames, email addresses, and roles via internal APIs, and can be leveraged to perform authenticated API requests. The vulnerability has been fixed in version 4.29.0.

Defensive priority

Defenders should prioritize verifying exposure and applying the patch to prevent exploitation.

Recommended defensive actions

• Verify exposure by checking if the installed version of ApostropheCMS is 4.28.0 or prior.
• Apply the patch by upgrading to ApostropheCMS version 4.29.0 or later.
• Monitor for suspicious activity, such as unusual API requests or changes to sensitive data.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description, CVSS score, and affected versions. The vulnerability has been fixed in version 4.29.0. Defenders should verify exposure by checking the installed version of ApostropheCMS and apply the patch by upgrading to version 4.29.0 or later. The CVE record and NVD entry also provide additional information on the vulnerability, including its CVSS score and affected versions.

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.