Ghost Head Template XSS via JSON-LD Injection

Executive Summary

This vulnerability affects Ghost CMS versions from 0.5.3 to before 6.50.0. It involves improper sanitization of data in the JSON-LD HTML tag generated by the {{ghost_head}} helper. An authenticated user with limited privileges can inject unescaped content that executes as script when rendered on a published page, potentially compromising a staff user's admin session.

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Detection Guidance

To detect this vulnerability, check your Ghost CMS version. If it is between 0.5.3 and below 6.50.0, it is vulnerable. Use commands like 'ghost version' or check your package.json for Ghost version. Inspect pages using {{ghost_head}} for unexpected script tags in JSON-LD output.

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Impact Analysis

An attacker could inject malicious scripts into pages viewed by staff users. If an admin views the affected page, their session could be compromised, leading to unauthorized access or control of the Ghost CMS instance.

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Compliance Impact

This XSS vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality requirements. For HIPAA, it may risk protected health information exposure. Compliance could be compromised if user data is accessed or altered due to the vulnerability.

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Mitigation Strategies

Immediately update Ghost CMS to version 6.50.0 or later. Remove or restrict access for untrusted users who could inject malicious content. Monitor admin sessions for unusual activity after updating.

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