Executive Summary

This vulnerability is a Stored Cross-Site Scripting (XSS) issue in the Evenium WordPress plugin, specifically in the 'evenium_single_event' shortcode. It occurs because the plugin does not properly sanitize or escape user-supplied attributes. Authenticated users with contributor-level access or higher can inject malicious scripts into pages via this shortcode. These scripts then execute whenever any user views the infected page, potentially compromising user data or site integrity. [1]

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Impact Analysis

The vulnerability allows attackers with contributor-level access to inject arbitrary JavaScript into pages, which executes in the context of users visiting those pages. This can lead to theft of session tokens, defacement, unauthorized actions performed on behalf of users, or other malicious activities. Because the injected scripts run in users' browsers, it can compromise user accounts and site security. [1]

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Detection Guidance

Detection of this vulnerability involves identifying the presence of the Evenium WordPress plugin version 1.3.11 or earlier and checking for usage of the 'evenium_single_event' shortcode that may contain malicious script injections. On the system, you can search for the plugin files and version by running commands like 'grep -r evenium_single_event /path/to/wordpress/wp-content/plugins/evenium' or checking the plugin version in the plugin directory. On the network, monitoring HTTP responses for script tags loading 'https://evenium.net/ng/js/widgets/web-widget.js' with suspicious or malformed URL parameters (especially those containing session tokens or injected scripts) can help detect exploitation attempts. Example commands include: 1) On the server: `grep -r 'evenium_single_event' /var/www/html/wp-content/plugins/evenium` 2) Using curl or wget to fetch pages and grep for the widget script: `curl -s https://yourwordpresssite.com/page | grep 'evenium.net/ng/js/widgets/web-widget.js'` 3) Network traffic inspection with tools like Wireshark or tcpdump filtering for requests to 'evenium.net' and analyzing query parameters for anomalies. [1]

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Mitigation Strategies

Immediate mitigation steps include: 1) Updating the Evenium plugin to a version later than 1.3.11 if available, where the vulnerability is fixed. 2) If an update is not available, temporarily disabling or removing the Evenium plugin to prevent exploitation. 3) Restricting contributor-level and above users from adding or editing content that uses the 'evenium_single_event' shortcode until the issue is resolved. 4) Implementing Web Application Firewall (WAF) rules to detect and block malicious payloads targeting the shortcode parameters. 5) Reviewing and sanitizing any existing content that uses the vulnerable shortcode to remove injected scripts. These steps reduce the risk of stored XSS attacks via the plugin's shortcode. [1]

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