What the vulnerability does
01Description
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.
Explanation of Vulnerability in Simple Terms
02Summary
ICS Calendar versions 12.0.9 and earlier contain a cross-site scripting (XSS) vulnerability. An attacker can inject malicious scripts that execute in a victim's browser when they visit a crafted link or page. The vulnerability affects the site's scope, meaning the injected script can access data and functionality beyond the vulnerable component itself. User interaction is required—the victim must click the malicious link or visit the attacker's page.
What an attacker can do
03Attacker Capabilities
Inject malicious scripts that run in visitors' browsers and steal session data or perform actions on their behalf.
Potential impact on your site
04Site Impact
Visitors' accounts and data are at risk if they click malicious links; your site's reputation may suffer if used to distribute malware.
Conditions required to exploit
05Prerequisites
Victim must click a malicious link or visit an attacker-controlled page; no authentication required.
Key dates
06Disclosure timeline
July 10, 2026
CVE published
