Stored XSS in EventPrime WordPress Plugin

Executive Summary

The EventPrime – Events Calendar, Bookings and Tickets plugin for WordPress has a Stored Cross-Site Scripting (XSS) vulnerability in the 'new_event_type_background_color' parameter. This vulnerability exists in all versions up to and including 4.3.4.2 due to insufficient input sanitization and output escaping.

Authenticated attackers with custom-level access or higher can inject arbitrary web scripts into pages. These scripts execute whenever a user accesses the injected page.

If the plugin's Guest Submissions setting (allow_submission_by_anonymous_user) is enabled, unauthenticated attackers can submit event types via the frontend form to exploit this vulnerability. If this setting is disabled, exploitation requires at least a subscriber-level authenticated account.

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Impact Analysis

This vulnerability allows attackers to inject malicious scripts that execute in the context of users visiting the affected pages. This can lead to theft of user credentials, session hijacking, or other malicious actions performed on behalf of the user.

Because the vulnerability can be exploited by unauthenticated users if guest submissions are enabled, it increases the risk of widespread exploitation.

The CVSS score of 7.2 indicates a high severity, meaning the impact on confidentiality and integrity is significant, though availability is not affected.

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Compliance Impact

The vulnerability allows authenticated attackers to inject arbitrary web scripts via stored cross-site scripting, potentially leading to unauthorized access or manipulation of user data.

Such unauthorized access or data manipulation could impact compliance with data protection regulations like GDPR and HIPAA, which require safeguarding personal data against unauthorized access and ensuring data integrity.

However, the provided information does not explicitly detail the direct compliance implications or specific regulatory impacts of this vulnerability.

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Detection Guidance

This vulnerability involves Stored Cross-Site Scripting via the 'new_event_type_background_color' parameter in the EventPrime plugin for WordPress. Detection involves checking if your WordPress installation uses the EventPrime plugin version 4.3.4.2 or earlier, and if the Guest Submissions setting (allow_submission_by_anonymous_user) is enabled.

To detect exploitation attempts or presence of injected scripts, you can search your WordPress database or web files for suspicious script tags or unusual content in event type background color fields.

• Use WP-CLI to check the plugin version: wp plugin list | grep eventprime
• Check the Guest Submissions setting in the WordPress admin or via database query.
• Search the database for suspicious script injections, for example using SQL: SELECT * FROM wp_postmeta WHERE meta_key LIKE '%new_event_type_background_color%' AND meta_value LIKE '%<script>%';
• Monitor web server logs for unusual POST requests to the event submission endpoints that include suspicious payloads.

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Mitigation Strategies

Immediate mitigation steps include updating the EventPrime plugin to a version later than 4.3.4.2 where the vulnerability is fixed.

If updating is not immediately possible, disable the Guest Submissions setting (allow_submission_by_anonymous_user) to prevent unauthenticated attackers from submitting event types.

Restrict user permissions to prevent low-level authenticated users (such as subscribers) from submitting or modifying event types.

Implement Web Application Firewall (WAF) rules to block suspicious input containing script tags in the 'new_event_type_background_color' parameter.

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