Summary
Relevanssi contains a stored cross-site scripting vulnerability in its handling of the comment parameter, allowing unauthenticated attackers to store scripts that execute in visitors' browsers. The issue becomes risky when comment indexing and comment highlighting are enabled and a visitor opens a matching singular-page permalink containing the highlight query parameter.
Relevanssi contains a stored cross-site scripting vulnerability in its handling of the comment parameter, allowing unauthenticated attackers to store scripts that execute in visitors' browsers. The issue becomes risky when comment indexing and comment highlighting are enabled and a visitor opens a matching singular-page permalink containing the highlight query parameter.
Affected context
The vulnerability occurs in WordPress sites using the Relevanssi search plugin when both comment indexing and comment highlighting are enabled. An injected value may be retained and later rendered on a singular page reached through a Relevanssi search-result permalink with the relevant highlight query parameter. The script executes when another user visits the affected page.
The vulnerability occurs in WordPress sites using the Relevanssi search plugin when both comment indexing and comment highlighting are enabled. An injected value may be retained and later rendered on a singular page reached through a Relevanssi search-result permalink with the relevant highlight query parameter. The script executes when another user visits the affected page.
Exploit preconditions
- Attack surface: Relevanssi search-result and highlighting functionality in a WordPress site
- Required access: No authentication is required to submit the relevant input
- Configuration requirement: Comment indexing and comment highlighting must both be enabled
- Trigger point: A visitor must access an affected singular page through a Relevanssi search-result permalink carrying the highlight query parameter
- Why exploitation is possible: The
commentparameter is insufficiently sanitized and later rendered without adequate context-aware output escaping
- Attack surface: Relevanssi search-result and highlighting functionality in a WordPress site
- Required access: No authentication is required to submit the relevant input
- Configuration requirement: Comment indexing and comment highlighting must both be enabled
- Trigger point: A visitor must access an affected singular page through a Relevanssi search-result permalink carrying the highlight query parameter
- Why exploitation is possible: The
commentparameter is insufficiently sanitized and later rendered without adequate context-aware output escaping
Why this happens
The underlying bug is insufficient validation or sanitization of user-controlled comment-related input combined with inadequate output encoding. When the value is stored or propagated into a search-result highlighting context, it can be interpreted as browser-executable markup or script rather than displayed as text. This behavior maps to CWE-79: Improper Neutralization of Input During Web Page Generation, commonly known as cross-site scripting.
The underlying bug is insufficient validation or sanitization of user-controlled comment-related input combined with inadequate output encoding. When the value is stored or propagated into a search-result highlighting context, it can be interpreted as browser-executable markup or script rather than displayed as text. This behavior maps to CWE-79: Improper Neutralization of Input During Web Page Generation, commonly known as cross-site scripting.
Potential impact
- Arbitrary JavaScript may execute in a visitor's browser
- Attackers could alter visible page content or present deceptive forms
- Session-context actions may be performed where browser privileges permit
- Sensitive information accessible to the affected page could be exposed
- Visitors could be redirected to malicious or phishing content
- Arbitrary JavaScript may execute in a visitor's browser
- Attackers could alter visible page content or present deceptive forms
- Session-context actions may be performed where browser privileges permit
- Sensitive information accessible to the affected page could be exposed
- Visitors could be redirected to malicious or phishing content
General mitigation guidance
Mitigation generally focuses on treating comment and search parameters as untrusted data throughout their full lifecycle.
Common defensive patterns include:
- Applying context-aware output encoding immediately before rendering values in HTML, attributes, URLs, or scripts
- Using allowlisted input validation and reducing the amount of user-controlled data accepted by highlighting features
- Ensuring stored values are sanitized according to their intended rendering context rather than relying on generic filtering
- Disabling comment indexing or comment highlighting when those features are not required
- Applying restrictive Content Security Policy controls as defense in depth
- Limiting administrative and editorial privileges to reduce the consequences of stored content abuse
Mitigation generally focuses on treating comment and search parameters as untrusted data throughout their full lifecycle.
Common defensive patterns include:
- Applying context-aware output encoding immediately before rendering values in HTML, attributes, URLs, or scripts
- Using allowlisted input validation and reducing the amount of user-controlled data accepted by highlighting features
- Ensuring stored values are sanitized according to their intended rendering context rather than relying on generic filtering
- Disabling comment indexing or comment highlighting when those features are not required
- Applying restrictive Content Security Policy controls as defense in depth
- Limiting administrative and editorial privileges to reduce the consequences of stored content abuse
How teams detect issues like this
Organizations can identify similar issues through:
- Static analysis rules for unescaped output of request parameters, comment data, and search-highlight values
- Code review checks that trace user-controlled input from request handling through storage, transformation, and rendering
- Tests that verify special characters remain encoded in every output context
- Dynamic testing of search-result permalinks and highlighting functionality with inert XSS markers
- Policy enforcement requiring context-specific escaping and security tests for plugin configuration combinations
- Neutral automated code-review or application-security tools that flag common unsafe output patterns
Organizations can identify similar issues through:
- Static analysis rules for unescaped output of request parameters, comment data, and search-highlight values
- Code review checks that trace user-controlled input from request handling through storage, transformation, and rendering
- Tests that verify special characters remain encoded in every output context
- Dynamic testing of search-result permalinks and highlighting functionality with inert XSS markers
- Policy enforcement requiring context-specific escaping and security tests for plugin configuration combinations
- Neutral automated code-review or application-security tools that flag common unsafe output patterns
Sources
| Source | Link |
|---|---|
| github. | github.com/ |
| plugins. | plugins.trac.wordpress.org/ |
| plugins. | plugins.trac.wordpress.org/ |
| plugins. | plugins.trac.wordpress.org/ |
| plugins. | plugins.trac.wordpress.org/ |
| plugins. | plugins.trac.wordpress.org/ |
| plugins. | plugins.trac.wordpress.org/ |
| wordfence. | wordfence.com/ |
