CVE-2018-19785 in PHP-Proxy
Summary
by MITRE
PHP-Proxy through 5.1.0 has Cross-Site Scripting (XSS) via the URL field in index.php.
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Analysis
by VulDB Data Team • 06/01/2026
The vulnerability identified as CVE-2018-19785 affects PHP-Proxy versions through 5.1.0 and represents a critical cross-site scripting flaw that resides within the application's URL handling mechanism. This vulnerability specifically manifests in the index.php file where user input from the URL field is not properly sanitized or validated before being rendered back to the user interface. The flaw allows malicious actors to inject arbitrary JavaScript code into the application's response, potentially enabling them to execute scripts in the context of other users who visit the compromised page. The vulnerability stems from inadequate input validation and output encoding practices, where the proxy application fails to properly escape or filter user-supplied URL parameters before displaying them to end users. This type of vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is one of the most prevalent and dangerous web application security flaws according to the CWE database.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious websites. When an attacker crafts a specially formatted URL containing malicious script code and convinces a victim to click on it through phishing or social engineering tactics, the script executes in the victim's browser context with the privileges of the authenticated user. The proxy application's nature as an intermediary between users and external web resources makes this vulnerability particularly dangerous as it can be leveraged to bypass security controls or access restricted resources. According to ATT&CK framework, this vulnerability maps to T1059.007 for scripting and T1566 for social engineering, as it requires user interaction to be effective and can be used to establish persistent access through session manipulation.
The technical exploitation of this vulnerability requires minimal effort as attackers only need to construct a malicious URL containing JavaScript code within the proxy's URL parameter field. The vulnerability exists because the application does not implement proper output encoding or sanitization when rendering user-provided URLs back to the browser interface. This flaw can be exploited through various methods including direct injection of script tags, event handlers, or more sophisticated techniques such as using javascript: protocol handlers. The vulnerability is particularly concerning in environments where the proxy is used for legitimate purposes such as accessing restricted corporate resources or bypassing content filters, as it could be used to compromise user sessions or exfiltrate sensitive information. Security professionals should note that this vulnerability is a classic example of how simple input validation failures can lead to severe security consequences, and it highlights the importance of implementing comprehensive defense-in-depth strategies including proper input sanitization, output encoding, and regular security assessments. Organizations using PHP-Proxy versions through 5.1.0 should immediately implement mitigations including input validation, output encoding, and application updates to prevent exploitation of this vulnerability.