CVE-2021-4363 in WP Quick FrontEnd Editor Plugin
Summary
by MITRE • 06/07/2023
The WP Quick FrontEnd Editor plugin for WordPress is vulnerable to Reflected Cross-Site Scripting in versions up to, and including, 5.5 due to insufficient input sanitization and output escaping on the 'save_content_front' function that uses print_r on the user-supplied $_REQUEST values . This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.
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Analysis
by VulDB Data Team • 04/09/2026
The WP Quick FrontEnd Editor plugin for WordPress presents a significant security vulnerability classified as CVE-2021-4363, affecting versions up to and including 5.5. This vulnerability manifests as a reflected cross-site scripting flaw that exploits inadequate input sanitization and output escaping mechanisms within the plugin's codebase. The vulnerability specifically targets the 'save_content_front' function which employs print_r to process user-supplied $_REQUEST values without proper sanitization, creating an exploitable vector for malicious code injection.
The technical flaw resides in the plugin's failure to adequately validate and escape user input before rendering it within web pages. When the 'save_content_front' function processes $_REQUEST parameters through print_r, it does not implement proper output escaping mechanisms that would prevent malicious scripts from being executed in the context of a victim's browser. This reflects a fundamental weakness in the plugin's security architecture that aligns with CWE-79, which describes improper neutralization of input during web page generation, commonly known as cross-site scripting vulnerabilities.
The operational impact of this vulnerability is particularly concerning as it affects unauthenticated attackers who can exploit the flaw without requiring any prior access credentials or privileges. Attackers can craft malicious URLs containing script payloads that, when clicked by unsuspecting users, would execute the injected code within the user's browser context. This makes the vulnerability highly dangerous in practice since it can be delivered through social engineering tactics such as phishing emails, malicious links in forums, or compromised websites that direct users to exploit the vulnerable plugin endpoint.
The vulnerability's exploitation pathway follows standard XSS attack patterns where an attacker crafts a malicious request that gets reflected back to the victim's browser. When the victim clicks on the crafted link, the browser executes the injected script, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The reflected nature of the vulnerability means that the malicious payload is not stored on the server but rather reflected back in the HTTP response, making it harder to detect through traditional server-side scanning methods.
Security practitioners should implement immediate mitigations including updating to the latest plugin version where the vulnerability has been patched, implementing proper input validation and output escaping mechanisms, and deploying web application firewalls that can detect and block suspicious script injection patterns. The vulnerability also highlights the importance of following secure coding practices such as those outlined in the OWASP Top Ten and MITRE ATT&CK framework, particularly focusing on defensive coding techniques that prevent XSS vulnerabilities through proper input sanitization and output encoding. Organizations should also consider implementing Content Security Policy headers as an additional defense-in-depth measure to limit the execution of unauthorized scripts on their WordPress installations.