CVE-2023-6561 in Featured Image from URL Plugin
Summary
by MITRE • 01/11/2024
The Featured Image from URL (FIFU) plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the featured image alt text in all versions up to, and including, 4.5.3 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/11/2026
The Featured Image from URL plugin for WordPress presents a significant security vulnerability classified as CVE-2023-6561, which manifests as a stored cross-site scripting flaw affecting versions up to and including 4.5.3. This vulnerability specifically targets the plugin's handling of featured image alt text fields, creating a persistent threat vector that can be exploited by authenticated attackers possessing contributor-level privileges or higher. The flaw represents a critical weakness in the plugin's input validation and output escaping mechanisms, allowing malicious actors to inject malicious scripts that persist within the plugin's data storage.
The technical implementation of this vulnerability stems from inadequate sanitization of user-supplied input within the alt text field of featured images. When administrators or contributors upload featured images using external URLs, they can specify alt text that should normally be treated as plain text. However, the plugin fails to properly sanitize this input before storing it in the database, and subsequently fails to adequately escape the output when rendering the alt text in web pages. This dual failure creates an environment where malicious JavaScript code can be stored and executed whenever the affected page is loaded, making it a classic stored XSS vulnerability that operates through the web application's legitimate data processing pathways.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to perform various malicious activities through the compromised WordPress installation. An attacker with contributor privileges can inject scripts that steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. This vulnerability undermines the security model of WordPress by allowing users with relatively low privileges to compromise the entire site's integrity, potentially leading to full site takeover, data exfiltration, or the establishment of persistent backdoors. The stored nature of the vulnerability means that once injected, the malicious scripts will execute automatically whenever any user accesses the affected pages, making detection and remediation challenging.
Mitigation strategies for CVE-2023-6561 should prioritize immediate plugin updates to versions that address the sanitization and escaping flaws. Organizations should implement comprehensive input validation measures that filter and sanitize all user-supplied data before storage, particularly focusing on HTML and JavaScript content. The principle of least privilege should be enforced by restricting contributor-level access to plugin configuration settings where possible, and implementing additional security layers such as content security policies that prevent execution of unauthorized scripts. Regular security audits of plugin installations should include verification of proper input sanitization and output escaping mechanisms, with monitoring for suspicious user activity that might indicate exploitation attempts. This vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and represents a clear violation of ATT&CK technique T1548.001, which covers privilege escalation through exploitation of application vulnerabilities. Organizations should also consider implementing web application firewalls and regular security scanning to detect and prevent exploitation attempts of similar vulnerabilities in their WordPress environments.