CVE-2021-3124 in Custom Global Variables Plugin
Summary
by MITRE • 02/26/2021
Stored cross-site scripting (XSS) in form field in robust.systems product Custom Global Variables v 1.0.5 allows a remote attacker to inject arbitrary code via the vars[0][name] field.
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Analysis
by VulDB Data Team • 03/05/2021
The vulnerability identified as CVE-2021-3124 represents a critical stored cross-site scripting flaw within the Custom Global Variables plugin version 1.0.5 developed by robust.systems. This security weakness exists in the form field processing mechanism where user input is not adequately sanitized before being stored and subsequently rendered back to users. The specific attack vector targets the vars[0][name] parameter, which serves as an entry point for malicious actors to inject persistent malicious scripts into the application's data storage system.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding practices within the plugin's backend processing logic. When administrators or users submit form data containing the vars[0][name] field, the application fails to properly sanitize or escape special characters that could be interpreted as HTML or JavaScript code. This oversight creates a persistent XSS condition where malicious scripts become permanently stored within the application's database and execute whenever the affected data is retrieved and displayed in user interfaces. The stored nature of this vulnerability means that the malicious payload remains active even after the initial injection point, making it particularly dangerous for long-term exploitation.
From an operational impact perspective, this vulnerability presents significant risks to organizations using the affected plugin as part of their web application infrastructure. Attackers can leverage this flaw to hijack user sessions, steal sensitive information, manipulate data, or redirect users to malicious websites. The persistence of stored XSS attacks allows threat actors to maintain access to compromised systems over extended periods, potentially enabling more sophisticated attacks such as credential theft, privilege escalation, or data exfiltration. The vulnerability affects not only the immediate users of the plugin but could also compromise the broader web application ecosystem if the plugin is integrated with other systems or if the malicious scripts can be used to exploit additional vulnerabilities within the same domain.
Organizations should implement immediate mitigations including input validation and output encoding mechanisms to prevent malicious code injection into form fields. The recommended approach involves sanitizing all user-supplied data before storage and properly encoding output to prevent script execution in web contexts. This aligns with established security practices outlined in CWE-79, which specifically addresses cross-site scripting vulnerabilities, and follows the ATT&CK framework's technique T1059.001 for command and scripting interpreter. Additionally, administrators should consider implementing web application firewalls, content security policies, and regular security audits to detect and prevent similar vulnerabilities. The most effective long-term solution involves upgrading to patched versions of the plugin, ensuring all input fields undergo proper validation, and establishing comprehensive security testing procedures that include automated scanning for XSS vulnerabilities.