CVE-2025-5699 in Developer Formatter Plugin
Summary
by MITRE • 06/06/2025
The Developer Formatter plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Custom CSS in all versions up to, and including, 2015.0.2.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level access, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.
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Analysis
by VulDB Data Team • 06/06/2025
The CVE-2025-5699 vulnerability resides within the Developer Formatter plugin for WordPress, specifically targeting versions up to and including 2015.0.2.1. This flaw represents a critical stored cross-site scripting vulnerability that leverages insufficient input sanitization and output escaping mechanisms. The vulnerability is particularly concerning because it requires only administrator-level access to exploit, making it a prime target for attackers who have gained elevated privileges within WordPress installations. The flaw manifests through the Custom CSS functionality, which serves as an entry point for malicious script injection that persists across user sessions.
The technical exploitation of this vulnerability occurs within multi-site WordPress installations where unfiltered_html has been disabled, creating a specific attack surface that security professionals must monitor closely. The vulnerability's classification aligns with CWE-79, which addresses Cross-Site Scripting flaws, and demonstrates how improper input validation can lead to persistent script execution. Attackers can inject malicious JavaScript code through the Custom CSS field, which then executes whenever any user accesses pages containing the injected content. This stored nature of the vulnerability means that the malicious scripts remain persistent until manually removed, potentially affecting all users who encounter the compromised pages.
The operational impact of CVE-2025-5699 extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities including credential theft, session hijacking, and data exfiltration. The vulnerability's restriction to multi-site installations with disabled unfiltered_html creates a specific attack scenario that differs from typical WordPress XSS vulnerabilities, making it particularly relevant for organizations running complex WordPress network configurations. This limitation means that the vulnerability's exploitation is more controlled and requires specific environmental conditions, yet it still represents a significant security risk for affected installations.
Mitigation strategies for this vulnerability should prioritize immediate plugin updates to versions that address the input sanitization and output escaping deficiencies. Organizations should also implement strict access controls and regularly audit administrator privileges to minimize the risk of unauthorized access. The ATT&CK framework's T1078 technique for Valid Accounts and T1566 for Phishing highlight how such vulnerabilities can be leveraged in broader attack campaigns, emphasizing the need for comprehensive security monitoring. Additionally, implementing Content Security Policy headers and regular security scanning can provide additional layers of protection against similar vulnerabilities. The vulnerability underscores the critical importance of input validation and output escaping in web applications, particularly within content management systems where administrators have elevated privileges and can introduce persistent threats through seemingly benign features like custom CSS editors.