EventPrime WordPress Plugin Stored XSS via Background Color Parameter

The EventPrime – Events Calendar, Bookings and Tickets plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'new_event_type_background_color' parameter in all versions up to, and including, 4.3.4.2 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with custom-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the plugin's Guest Submissions setting (allow_submission_by_anonymous_user) to be enabled, which allows unauthenticated attackers to submit event types via the frontend form; when that setting is disabled, exploitation requires at minimum a subscriber-level authenticated account.

Casky was already ahead

This CVE exploits attack patterns that Casky's 322matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

The EventPrime – Events Calendar, Bookings and Tickets WordPress plugin contains a Stored Cross-Site Scripting (XSS) vulnerability in versions up to 4.3.4.2, affecting the 'new_event_type_background_color' parameter. Due to insufficient input sanitization and output escaping, authenticated users with custom-level access or higher can inject arbitrary JavaScript code that persists in the database. When other users visit pages containing the injected event type, the malicious script executes in their browsers, potentially leading to session hijacking, credential theft, or unauthorized actions performed on behalf of legitimate users. This vulnerability is particularly dangerous because it affects WordPress sites relying on EventPrime for event management, impacting administrators, event organizers, and website visitors alike.

Casky's 322 matched security skills leverage Claude AI with extended reasoning to detect the attack patterns underlying this vulnerability across MITRE ATT&CK techniques TA0001 (Initial Access) and TA0043 (Reconnaissance). Practitioners using Casky would identify findings related to CWE-79 violations where user-supplied input flows directly into stored page output without proper validation or HTML encoding. The platform's skills would flag instances where the 'new_event_type_background_color' parameter—or similar color/styling inputs—accepts script tags, event handlers (onclick, onerror), or encoded JavaScript payloads. Detection would surface suspicious parameter patterns, database queries storing unescaped content, and rendering contexts where user input appears in HTML attributes or script contexts without proper escaping mechanisms, enabling practitioners to remediate before exploitation occurs.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

322 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-13441.

Abuse of Public-Facing API: Mobile API Abuse

mobile security · low

Run

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

MITRE ATT&CK Techniques

TA0001 TA0043

Investigate the attack patterns behind CVE-2026-13441

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