Stored Cross-Site Scripting in Calendar WordPress Plugin

Executive Summary

This is a stored Cross-Site Scripting (XSS) vulnerability in the Calendar WordPress plugin before version 1.3.18. It occurs because the plugin does not properly escape user input in the event_link parameter, allowing Contributor-level users to inject malicious JavaScript into the Link field of an event. When visitors view the calendar, the injected script executes in their browsers, such as when hovering over the event link.

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Detection Guidance

Check if the Calendar WordPress plugin version is below 1.3.18. Log in as a Contributor and inspect event creation forms for the event_link parameter. Look for JavaScript code in the Link field of events.

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Impact Analysis

If you are a visitor viewing a calendar with this vulnerability, malicious JavaScript could execute in your browser without your knowledge. This could lead to theft of session cookies, redirection to phishing sites, or other malicious actions. If you are a WordPress site administrator, an attacker with Contributor access could exploit this to compromise your site or visitors.

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Compliance Impact

This vulnerability could lead to unauthorized access to user data, which may violate GDPR (data protection) and HIPAA (health information privacy) requirements. If exploited, it could result in data breaches, leading to legal penalties, reputational damage, and loss of trust. Organizations must address this to maintain compliance.

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Mitigation Strategies

Update the Calendar plugin to version 1.3.18 or later immediately. If updating is not possible, disable the plugin until a patch is applied. Review all events for suspicious JavaScript code in the Link field.

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