CVE-2021-4378 in WP Quick FrontEnd Editor Plugin
Summary
by MITRE • 06/07/2023
The WP Quick FrontEnd Editor plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 5.5 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with minimal permissions like subscribers, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 04/09/2026
The WP Quick FrontEnd Editor plugin for WordPress represents a critical security vulnerability classified as CVE-2021-4378, which affects versions up to and including 5.5. This vulnerability manifests as a stored cross-site scripting flaw that undermines the security posture of WordPress installations. The flaw occurs within the plugin's handling of user input and output rendering processes, creating an environment where malicious scripts can persist and execute automatically. The vulnerability's severity is amplified by the minimal permission requirements needed to exploit it, as even users with subscriber-level access can leverage this weakness to compromise the platform.
The technical root cause of this vulnerability stems from insufficient input sanitization mechanisms within the plugin's codebase. When users submit content through the front-end editor interface, the plugin fails to properly validate and sanitize the input data before storing it in the database. Additionally, the output escaping mechanisms are inadequate, meaning that stored content is not properly encoded when rendered back to users. This dual failure creates a persistent XSS vector where malicious scripts can be injected into the system and executed whenever affected pages are accessed. The vulnerability specifically targets the plugin's front-end editing functionality, making it particularly dangerous as it operates within the context of legitimate user interactions.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with a foothold for more sophisticated attacks within the WordPress environment. An authenticated attacker with subscriber permissions can inject malicious JavaScript code that executes whenever any user views the affected pages, potentially leading to session hijacking, data theft, or further exploitation. The stored nature of the vulnerability means that the malicious payloads persist long after initial injection, creating ongoing security risks that can affect multiple users over time. This vulnerability undermines the principle of least privilege and exposes the entire WordPress installation to potential compromise, particularly in multi-user environments where subscriber accounts may have unexpected access paths.
Security professionals should consider this vulnerability in the context of the CWE-79 weakness category, which specifically addresses cross-site scripting flaws in software applications. The ATT&CK framework categorizes this as a technique for code injection and privilege escalation, where attackers can leverage minimal user permissions to gain broader system access. Mitigation strategies should include immediate plugin updates to versions that address the sanitization and escaping deficiencies, along with implementing additional security measures such as content security policies and regular security audits. Organizations should also consider implementing web application firewalls to detect and block malicious script injection attempts, while ensuring that all WordPress installations maintain current security patches and follow secure coding practices to prevent similar vulnerabilities from emerging in the future.