CVE-2026-77186
Deferred Deferred - Pending Action

Stored XSS in My Calendar WordPress Plugin

Publication date: 2026-09-09

Last updated on: 2026-09-09

Assigner: Wordfence

Description
The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'fallback' Shortcode Attribute in all versions up to, and including, 3.8.3 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The bypass relies on hex-encoded shortcode attribute payloads (e.g. \x3cscript\x3e), which wp_kses_post cannot strip on save because they appear as literal backslash sequences rather than real HTML tags; WordPress core's shortcode_parse_atts() then calls stripcslashes() at render time, decoding the escapes into real angle brackets before they reach the unescaped sink.

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Meta Information

Published
2026-09-09
Last Modified
2026-09-09
Generated
2026-09-30
AI Q&A
2026-09-09
EPSS Evaluated
2026-09-27
NVD
CVE-2026-77186
EUVD
EUVD-2026-74603

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
joedolson my_calendar to 3.8.3 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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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 My Calendar WordPress plugin has a stored Cross-Site Scripting (XSS) vulnerability in versions up to 3.8.3. It occurs due to insufficient input sanitization and output escaping in the 'fallback' shortcode attribute. Authenticated attackers with contributor-level access or higher can inject malicious scripts via hex-encoded payloads that bypass WordPress's wp_kses_post sanitization. These scripts execute when users access infected pages.

Detection Guidance

Check for the My Calendar plugin version up to 3.8.3 in WordPress installations. Inspect pages using the fallback shortcode for hex-encoded payloads like \x3cscript\x3e. Use WordPress admin to review contributor-level user activity and modified pages.

Impact Analysis

This vulnerability allows attackers to inject malicious scripts into your WordPress site. If exploited, these scripts could steal user data, hijack sessions, or deface your website. Users visiting compromised pages may have their sensitive information exposed or be redirected to malicious sites.

Compliance Impact

This XSS vulnerability could lead to data breaches, violating GDPR's data protection requirements and HIPAA's security rules for protected health information. If user data is compromised through this exploit, organizations may face regulatory fines, legal liabilities, and reputational damage.

Mitigation Strategies

Update the My Calendar plugin to the latest version beyond 3.8.3. Remove or sanitize any injected scripts in existing pages. Restrict contributor-level access to trusted users only.

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