CVE-2026-77186 My Calendar <= 3.8.3 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'fallback' Shortcode Attribute
Authenticated contributors can inject arbitrary scripts via hex-encoded shortcode attributes, leading to stored XSS execution for other users.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-77186?
CVE-2026-77186 is a medium-severity cross-site scripting vulnerability in joedolson My Calendar – Accessible Event Manager, published on 9 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-77186?
How do I fix CVE-2026-77186?
No fix has been published for CVE-2026-77186 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-77186 being exploited?
There is no known exploitation of CVE-2026-77186 in the wild and no public exploit code.
Sources
Also known as GHSA-588q-hr78-m65w.