CVE-2023-4520 in FV Flowplayer Video Player Plugin
Summary
by MITRE • 08/25/2023
The FV Flowplayer Video Player plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘_fv_player_user_video’ parameter saved via the 'save' function hooked via init, and the plugin is also vulnerable to Arbitrary Usermeta Update via the 'save' function in versions up to, and including, 7.5.37.7212 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page, and makes it possible to update the user metas arbitrarily, but the meta value can only be a string.
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Analysis
by VulDB Data Team • 09/20/2023
The CVE-2023-4520 vulnerability affects the FV Flowplayer Video Player plugin for WordPress, specifically targeting versions up to and including 7.5.37.7212. This security flaw represents a critical concern for WordPress site administrators as it exposes the platform to multiple attack vectors through improper input validation and sanitization mechanisms. The vulnerability manifests through two primary attack paths that together create a significant risk for compromised WordPress installations.
The core technical flaw lies in the plugin's handling of user input through the '_fv_player_user_video' parameter within the 'save' function that is hooked via the init action. This function fails to properly sanitize and escape user-supplied data before storing it in the WordPress database, creating a persistent cross-site scripting vulnerability. The stored XSS vulnerability occurs because the plugin does not implement adequate input validation or output escaping mechanisms when processing the user_video parameter, allowing attackers to inject malicious JavaScript code that persists in the database and executes whenever affected pages are accessed.
The second vulnerability component involves arbitrary usermeta update capabilities that stem from the same flawed save function implementation. Attackers can exploit this weakness to manipulate user metadata values, though the implementation restricts meta values to string data types. This creates a scenario where unauthenticated attackers can modify user profiles and potentially escalate privileges or manipulate user sessions. The vulnerability's impact extends beyond simple XSS execution as it provides a pathway for attackers to modify user information and potentially gain unauthorized access to user accounts.
From a cybersecurity perspective, this vulnerability aligns with CWE-79 (Cross-Site Scripting) and CWE-20 (Improper Input Validation) classifications, representing a classic example of how insufficient data sanitization can create persistent security risks. The ATT&CK framework categorizes this as a web application vulnerability that could enable initial access or privilege escalation, particularly through the usermeta manipulation component. The stored nature of the XSS vulnerability means that once an attacker successfully injects malicious code, it will execute automatically for any user who accesses the affected pages, making it particularly dangerous for high-traffic WordPress sites.
The operational impact of this vulnerability extends beyond immediate code execution risks to include potential session hijacking, credential theft, and further exploitation opportunities. Attackers could use the XSS capability to steal administrator credentials, redirect users to malicious sites, or inject additional malicious scripts that could compromise the entire WordPress installation. The arbitrary usermeta update vulnerability compounds these risks by providing attackers with additional means to manipulate user accounts and potentially create persistent backdoors within the WordPress environment.
Mitigation strategies should include immediate plugin updates to versions that address these vulnerabilities, though administrators should also implement additional security measures such as input validation at the web application firewall level, regular security audits of plugin installations, and monitoring for suspicious usermeta changes. Network-level protections including content security policies and regular vulnerability scanning can help detect and prevent exploitation attempts. Additionally, administrators should consider implementing role-based access controls and regular security assessments to minimize the potential impact of such vulnerabilities in their WordPress environments.