Arbitrary Shortcode Execution in Easy Appointments WordPress Plugin

Executive Summary

The Easy Appointments WordPress plugin up to version 3.12.26 has a flaw in how it handles shortcode input during block rendering. It only checks the first tag of a user-supplied string against an allowlist but then processes the entire string, allowing contributors to execute any registered shortcode.

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Detection Guidance

To detect this vulnerability, check for unauthorized shortcode execution in WordPress. Inspect WordPress logs for suspicious shortcode usage, particularly from contributor-level users. Review plugin files for the Easy Appointments plugin version 3.12.26 or earlier. Use commands like grep to search for shortcode patterns in logs or database entries.

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Impact Analysis

An attacker with contributor-level access could exploit this to run arbitrary shortcodes, potentially leading to unauthorized actions like data theft, content manipulation, or other malicious activities depending on the shortcodes available.

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Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality principles or HIPAA's safeguards for protected health information if exploited.

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Mitigation Strategies

Update the Easy Appointments WordPress plugin to version 3.12.26 or later to address the shortcode validation issue.

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