CVE-2026-77186 json
My Calendar <= 3.8.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'fallback' Shortcode Attribute
published 2026-09-09 2 mo ago modified 2026-09-09 2 mo ago also EUVD-2026-74603
- cvss
- 6.4
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 29%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 2 mo ago
Exploit prediction
0.36% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.4 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N |
Affected products
- joedolson My Calendar – Accessible Event Manager
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
- Technology feeds
References
- github.com /joedolson/my-calendar/commit/89bbf7314fac84cdb89e520e8b7b6d69eee8dd3c
- wordfence.com /threat-intel/vulnerabilities/id/62c8fb1f-6cba-43cc-8aca-70812c29a63d?source=cve
- plugins.trac.wordpress.org /browser/my-calendar/trunk/my-calendar-widgets.php#L272
- plugins.trac.wordpress.org /browser/my-calendar/trunk/my-calendar-shortcodes.php#L114
- plugins.trac.wordpress.org /browser/my-calendar/trunk/my-calendar.php#L556
Sources
- CVE List CVE-2026-77186
- NVD CVE-2026-77186
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.