CVE-2026-15984
Received Received - Intake

Stored XSS in QuickCal WordPress Plugin

Publication date: 2026-09-05

Last updated on: 2026-09-05

Assigner: Wordfence

Description
The QuickCal plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Custom Field Parameters in all versions up to, and including, 1.0.20 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 nonce guarding the unauthenticated booked_add_appt AJAX action is publicly embedded on any page rendering the booking calendar shortcode, making it trivially obtainable by unauthenticated attackers without any prior account or privilege.

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Meta Information

Published
2026-09-05
Last Modified
2026-09-05
Generated
2026-09-05
AI Q&A
2026-09-05
EPSS Evaluated
N/A
NVD
CVE-2026-15984
EUVD
EUVD-2026-71885

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
quickcal quickcal to 1.0.20 (inc)

Helpful Resources

Exploitability

CWE
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KEV
KEV Icon
CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

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Executive Summary

The QuickCal WordPress plugin up to version 1.0.20 has a stored cross-site scripting vulnerability. It allows unauthenticated attackers to inject malicious scripts via custom field parameters due to poor input sanitization and output escaping. These scripts execute when users view infected pages.

Detection Guidance

To detect this vulnerability, inspect WordPress sites using the QuickCal plugin up to version 1.0.20 for unauthorized script injections in custom field parameters. Check for unusual web scripts in pages rendered by the booking calendar shortcode. Review server logs for suspicious AJAX requests to the booked_add_appt endpoint.

Impact Analysis

Attackers could steal user sessions, redirect to malicious sites, or perform actions on behalf of users. Since the nonce for the AJAX action is publicly exposed, exploitation requires no prior access or privileges.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR (data protection) and HIPAA (health data security) requirements. Organizations using the plugin may face compliance breaches and legal penalties.

Mitigation Strategies

Immediately update the QuickCal plugin to the latest version beyond 1.0.20. Remove any unauthorized scripts from custom fields and pages. Implement input sanitization for all user-supplied data. Monitor for signs of exploitation and consider disabling the plugin temporarily if an update is unavailable.

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