joedolson My Calendar Plugin up to 3.8.3 on WordPress Shortcode shortcode_parse_atts fallback cross site scripting

Summaryinfo

A vulnerability was found in joedolson My Calendar Plugin up to 3.8.3. It has been declared as problematic. Impacted is the function shortcode_parse_atts of the component Shortcode Handler. Executing a manipulation of the argument fallback can lead to cross site scripting. This vulnerability appears as CVE-2026-77186. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability classified as problematic was found in joedolson My Calendar Plugin up to 3.8.3. This vulnerability affects the function shortcode_parse_atts of the component Shortcode Handler. The manipulation of the argument fallback with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at wordfence.com. This vulnerability was named CVE-2026-77186 since 08/20/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• WordPress Plugin

Vendor

• joedolson

Name

• My Calendar Plugin

Version

• 3.8.0
• 3.8.1
• 3.8.2
• 3.8.3

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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