Quill Forms - Security Vulnerability (CVE-2026-15664)

Q: Am I affected by this vulnerability?

You are affected if your site runs Quill Forms. No account is needed to exploit this, so a public site is reachable by anyone.

Q: How do I fix it?

Update Quill Forms to the latest available version. Where the vendor has not yet published a fix, remove or disable the plugin until they do. Until you can update, Request / payload inspection (WAF) in Hack Halt ProSecure contains this class of attack at the request layer.

Q: What can an attacker actually do?

This is a Cross-Site Scripting (XSS) flaw. An attacker who exploits it can run script in a visitor's browser, stealing sessions or planting an administrator account.

CVE-2026-15664

Vulnerability CVE-2026-15664 PLUGIN quill-forms HIGH

The Quill Forms | Conversational Multi Step Forms, Surveys & quizzes plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Multiple Choice 'Other' Value in all versions up to, and including, 5.7.1 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The injected script executes in the context of the WordPress admin results view, making administrators the primary target when reviewing submitted form entries.

CVE-2026-15664

HIGH CVSS 7.2 Published 2026-09-19 Updated 2026-09-21

AI Risk Elevated (72/100) Active Exploit: No strong signal Published Exploit: No public exploit references Priority: P3 Priority

Severity Band HIGH

CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Affected Components 3

Reference Links 10

AI Risk Engine Elevated (72/100)

Exploitability Medium

Active Exploitation No strong signal

Published Exploit Status No public exploit references

Threat Timeline

2026-09-19 CVE published and first recorded in the threat feed.
2026-09-21 Record updated with latest vulnerability metadata.
2026-09-22 AI technical context refreshed for mitigation and impact guidance.
Now Monitoring for follow-up changes, linked references, and new related CVEs.

AI Context

Machine-generated threat intelligence

AI Updated just now

AI enriched just now (2026-09-22 20:40 UTC)

Technical Summary

Potential Impact

Severity is HIGH (CVSS 7.2). Depending on deployment context, affected components may be exposed to unauthorized actions or data integrity risk.

Exploitability Assessment

Exploitability is assessed as Medium based on low-bar exploit prerequisites.

Primary risk drivers: low-bar exploit prerequisites

Mitigation Recommendations

Validate affected product versions, prioritize patching, and monitor references for vendor remediation guidance. If immediate patching is not possible, apply compensating controls and limit exposure of vulnerable surfaces.

Detection & Monitoring

Track authentication anomalies, unexpected file writes, and suspicious plugin API activity around affected components.

Business Impact Lens

AI risk score 72/100 (Elevated, Medium) with priority P3 Priority. Prioritize remediation where affected components process customer data, admin sessions, or Internet-exposed workflows.

Affected Products

Quill Forms PLUGIN · quill-forms Affected: >= 0, <= 5.7.1 Fixed version not specified

Quill Forms | Conversational Multi Step Forms, Surveys & quizzes PLUGIN · quill-forms-conversational-multi-step-forms-surveys-quizzes Affected: >= 0, <= 5.7.1 Fixed version not specified

Quillforms PLUGIN · quillforms Affected: >= 0, <= 5.7.1 Fixed version not specified

References

What to do about this

Patch promptly The consequence is significant even where an attacker needs a foothold first.

Fix it

Update Quill Forms to the latest available version.

Where the vendor has not published a fix yet, disable the plugin until they do.

Cannot update today? Request / payload inspection (WAF) in Hack Halt ProSecure blocks this class of attack before WordPress processes the request.

Inspect request parameters and bodies for injection, traversal and file-inclusion payloads, and refuse the request rather than logging it.

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Not sure if you are affected?

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