CVE-2026-18547 ultimatemember CVE debrief

Who should care

WordPress administrators, security teams, and users with subscriber-level access or above should assess exposure and prioritize remediation. This includes reviewing the affected versions, verifying the remediation status, and ensuring that compensating controls are in place for exposed systems.

Why it matters

CVE-2026-18547 allows authenticated attackers to inject web scripts, potentially impacting user interactions. Assess exposure and prioritize remediation for WordPress installations using the Ultimate Member plugin.

• Authenticated attackers can inject web scripts that execute when a user accesses an injected page
• Possible impact on user interactions with injected pages
• Requires verification of affected versions and remediation status

Technical summary

The Ultimate Member plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Textarea Profile Field with HTML Support (DOM Gadget via id Attribute) in all versions up to, and including, 2.12.1. This vulnerability allows authenticated attackers, with subscriber-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The vulnerability arises from insufficient input sanitization and output escaping, specifically with the wp_kses 'templates' allowlist permitting the id attribute on div elements without neutralizing unescaped quotes within its value.

Defensive priority

Assess exposure and prioritize remediation for WordPress installations using the Ultimate Member plugin, especially those allowing subscriber-level access or above.

Recommended defensive actions

• Inventory and assess exposure of WordPress installations using the Ultimate Member plugin
• Prioritize remediation for installations allowing subscriber-level access or above
• Monitor for suspicious activity and implement compensating controls
• Verify vendor remediation and apply patches
• 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

Evidence notes

The vulnerability exists in all versions up to, and including, 2.12.1 of the Ultimate Member plugin due to insufficient input sanitization and output escaping. The wp_kses 'templates' allowlist permits the id attribute on div elements but does not neutralize unescaped quotes within its value; when pickadate.js concatenates the stored id value into an HTML string via jQuery .html() on profile page load, the smuggled onfocus and autofocus attribute syntax breaks out of attribute context and executes as JavaScript. This issue allows for

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.