Insecure Direct Object Reference in Static Block WordPress Plugin

Detection Guidance

This vulnerability involves the Static Block plugin for WordPress allowing authenticated users with contributor-level access or higher to read arbitrary post contents by embedding a shortcode with an 'id' attribute referencing posts they should not access.

Detection can focus on monitoring for the use of the shortcode [static_block_content id="X"] in user-generated content or preview requests, especially from contributor-level users.

Since the vulnerability is exploited by embedding the shortcode in content and previewing it, you can search your WordPress database or logs for occurrences of the shortcode pattern.

• Use a database query to find posts or content containing the shortcode, for example in MySQL: SELECT ID, post_content FROM wp_posts WHERE post_content LIKE '%[static_block_content id="%'
• Check web server access logs for requests that include preview parameters combined with the shortcode usage.
• Monitor user activity logs for contributor-level users creating or previewing content containing the shortcode.

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Executive Summary

The Static Block plugin for WordPress has a vulnerability called Insecure Direct Object Reference (IDOR) in all versions up to and including 2.2.

This happens because the shortcode handler static_block_content() retrieves a post using an attacker-supplied 'id' attribute without verifying the post's status (such as private, draft, or pending) or whether the user has permission to view it.

As a result, authenticated users with contributor-level access or higher can read the contents of arbitrary posts, including private and draft static blocks or other post types created by administrators, by embedding the shortcode [static_block_content id="X"] in their own content and previewing it.

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Impact Analysis

This vulnerability allows attackers with contributor-level access or above to read private or draft content that they should not normally be able to access.

This could lead to unauthorized disclosure of sensitive or confidential information contained in private posts or static blocks created by administrators.

Since the vulnerability does not allow modification or deletion, the impact is limited to confidentiality loss.

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Compliance Impact

This vulnerability allows authenticated users with contributor-level access or higher to read the contents of arbitrary posts, including private and draft static blocks created by administrators, without proper authorization checks.

Such unauthorized access to potentially sensitive or private information could lead to violations of data protection standards and regulations like GDPR or HIPAA, which require strict controls on access to personal or sensitive data.

Therefore, exploitation of this vulnerability may result in non-compliance with these regulations due to improper access control and potential exposure of protected information.

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Mitigation Strategies

To mitigate this vulnerability, immediate steps include:

• Update the Static Block plugin to a version later than 2.2 where the vulnerability is fixed.
• Restrict contributor-level and above users from embedding the [static_block_content] shortcode until the plugin is updated.
• Implement additional access controls or filters to verify post status and user capabilities before rendering post content via the shortcode.
• Monitor and audit user content for unauthorized shortcode usage.

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