CVE-2021-47914 in PHP Melody
Summary
by MITRE • 02/01/2026
PHP Melody version 3.0 contains a persistent cross-site scripting vulnerability in the edit-video.php submitted parameter that allows remote attackers to inject malicious script code. Attackers can exploit this vulnerability to execute arbitrary JavaScript, potentially leading to session hijacking, persistent phishing, and manipulation of application modules.
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Analysis
by VulDB Data Team • 02/12/2026
The vulnerability identified as CVE-2021-47914 represents a critical persistent cross-site scripting flaw within PHP Melody version 3.0, specifically affecting the edit-video.php component. This weakness resides in the handling of the submitted parameter, creating an avenue for remote attackers to inject malicious JavaScript code into the application's processing pipeline. The vulnerability stems from insufficient input validation and output encoding mechanisms that fail to properly sanitize user-supplied data before it is processed and stored within the system's database.
The technical exploitation of this vulnerability occurs when an attacker submits malicious script code through the edit-video.php interface, which then gets stored persistently within the application's backend storage. This persistent nature means that the malicious payload remains embedded in the system and executes whenever the affected content is accessed by legitimate users or administrators. The flaw operates under CWE-79 which categorizes cross-site scripting vulnerabilities as weaknesses in input validation and output encoding, specifically targeting the failure to properly escape or filter user-controllable data before it is rendered in web pages. The vulnerability aligns with ATT&CK technique T1566.001 which describes the use of malicious content to establish initial access through web-based attacks.
The operational impact of this vulnerability extends beyond simple script execution, creating substantial risks for system security and user privacy. Attackers can leverage this weakness to hijack user sessions by stealing session cookies and credentials, effectively impersonating legitimate users within the application. The persistent nature of the vulnerability enables attackers to deploy long-term phishing campaigns where malicious links or content remain active within the application interface, potentially deceiving users into revealing sensitive information. Additionally, the ability to execute arbitrary JavaScript code allows attackers to manipulate application modules, potentially altering functionality, accessing restricted areas, or even escalating privileges within the system. This vulnerability particularly threatens content management systems where administrators frequently interact with user-generated content, as the malicious scripts could execute with elevated privileges when accessed by administrative users.
Mitigation strategies for CVE-2021-47914 should prioritize immediate patching of the affected PHP Melody version 3.0 to address the input validation and output encoding deficiencies. Organizations must implement comprehensive input sanitization measures that validate and filter all user-supplied data before processing, particularly focusing on the edit-video.php component and similar interfaces. Output encoding should be enforced for all dynamic content rendered in web interfaces, ensuring that any user-controllable data is properly escaped to prevent script execution. Security headers including Content Security Policy should be implemented to limit the execution of unauthorized scripts within the application environment. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other application components, while input validation should be strengthened through the implementation of allowlists for expected data formats and character sets. Network monitoring should be enhanced to detect unusual data submission patterns that may indicate exploitation attempts, and user access controls should be reviewed to minimize the impact of potential compromise through the implementation of principle of least privilege.