ICS Calendar <= 12.0.9 - Reflected Cross-Site Scripting via 'htmltagtitle' Parameter
Strategic Overview
- Status
- Patched in 12.0.9.2
- Affected Plugin
- ICS Calendar
- Affected Version
<= 12.0.9- CVSS
- 6.1Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2026-9838
At a glance
CVE-2026-9838 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the ICS Calendar WordPress plugin, affecting versions <= 12.0.9. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 12.0.9.2; sites on affected versions should update now. Disclosed July 2026, reported by Khanh Nguyen.
Vulnerability Overview
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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
ICS Calendar <= 12.0.9 carries this weakness at htmltagtitle, and reaching it takes a caller who can reach the endpoint. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.
Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For ICS Calendar the fix is 12.0.9.2: builds <= 12.0.9 are affected, anything from 12.0.9.2 onward is not.
Remediation
Update to version 12.0.9.2, or a newer patched version
How does WordSec protect against this?
The attempt arrives as an ordinary request to ICS Calendar: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: ICS Calendar 12.0.9.2 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Related records
Same weakness class
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