CVE-2026-9838 ICS Calendar <= 12.0.9 - Reflected Cross-Site Scripting via 'htmltagtitle' Parameter
Unauthenticated attackers can inject arbitrary scripts via the htmltagtitle parameter in the ICS Calendar WordPress plugin, requiring user interaction to execute.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-9838?
CVE-2026-9838 is a medium-severity cross-site scripting vulnerability in room34 ICS Calendar, published on 10 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
The ICS Calendar plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'htmltagtitle' parameter in all versions up to, and including, 12.0.9 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. The vulnerability is reachable via the unauthenticated wp_ajax_nopriv_r34ics_ajax AJAX action, which accepts attacker-controlled js_args values merged over stored shortcode configuration without nonce verification, allowing the htmltagtitle key to bypass the normal shortcode allowlist check.
Weakness: CWE-79
Which versions are affected by CVE-2026-9838?
How do I fix CVE-2026-9838?
No fix has been published for CVE-2026-9838 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-2026-9838 being exploited?
There is no known exploitation of CVE-2026-9838 in the wild and no public exploit code.
Sources
Also known as GHSA-x463-v9cq-m85h.