CVE-2017-12813 in File Sharing Script
Summary
by MITRE
PHPJabbers File Sharing Script 1.0 has stored XSS in the comments section.
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Analysis
by VulDB Data Team • 12/18/2019
The vulnerability identified as CVE-2017-12813 represents a critical stored cross-site scripting flaw within the PHPJabbers File Sharing Script version 1.0. This security weakness resides in the comments section of the web application, where user input is not properly sanitized before being stored and subsequently rendered back to other users. The vulnerability enables attackers to inject malicious scripts that persist in the application's database, making it a stored XSS vulnerability rather than a reflected one. Such flaws are particularly dangerous because they can affect multiple users over time without requiring them to click on malicious links, as the malicious code is already present in the application's data storage.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding practices within the comments processing functionality. When users submit comments through the file sharing interface, the application fails to properly escape or filter special characters that could be interpreted as HTML or JavaScript code. This allows attackers to embed malicious scripts such as javascript:alert(document.cookie) or more sophisticated payload delivery mechanisms that can exfiltrate user session cookies, perform unauthorized actions on behalf of victims, or redirect them to malicious sites. The vulnerability specifically affects the comment submission and display functionality, where the application stores user-generated content without proper sanitization before presenting it to other users who view the comments section.
The operational impact of this stored XSS vulnerability extends beyond simple data theft or defacement. Attackers can leverage this flaw to hijack user sessions, potentially gaining administrative privileges or access to sensitive file sharing operations. The persistence of the malicious code means that every user who views the affected comments section becomes a potential victim, creating a scalable attack vector that can compromise numerous users simultaneously. Additionally, the vulnerability can be used to deliver malware through drive-by download techniques or to perform phishing attacks by redirecting users to malicious domains. This type of vulnerability directly violates security principles outlined in the OWASP Top Ten, specifically targeting the injection category of web application vulnerabilities.
Mitigation strategies for CVE-2017-12813 require immediate implementation of proper input validation and output encoding mechanisms. The application should employ comprehensive sanitization of all user inputs before storage, utilizing libraries such as HTMLPurifier or similar content security measures. Implementing Content Security Policy headers can provide additional defense-in-depth protection against malicious script execution. The principle of least privilege should be enforced, ensuring that comments are properly validated against a whitelist of allowed characters and HTML tags. Security patches should be applied immediately to update the PHPJabbers File Sharing Script to a version that addresses this vulnerability, as the affected version is likely to contain other unpatched security issues. Organizations should also implement regular security assessments and penetration testing to identify similar vulnerabilities in their web applications. This vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and represents a clear violation of the ATT&CK technique T1059.007 for command and scripting interpreter, specifically targeting the execution of malicious scripts within user browsers.