CVE-2018-16050 in Community Edition
Summary
by MITRE
An issue was discovered in GitLab Community and Enterprise Edition 11.1.x before 11.1.5 and 11.2.x before 11.2.2. There is Persistent XSS in the Merge Request Changes View.
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Analysis
by VulDB Data Team • 05/22/2023
The vulnerability identified as CVE-2018-16050 represents a critical persistent cross-site scripting flaw within GitLab's merge request changes view functionality. This security weakness affects both Community and Enterprise editions of GitLab, specifically targeting versions 11.1.x prior to 11.1.5 and 11.2.x prior to 11.2.2. The flaw resides in how the application processes and displays user-generated content within the merge request changes view, creating an environment where malicious actors can inject persistent XSS payloads that execute in the context of other users' browsers.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within GitLab's merge request changes view component. When users submit merge requests containing specially crafted malicious content, the application fails to properly sanitize or escape this input before rendering it in the user interface. This insufficient sanitization allows attackers to inject JavaScript code that persists in the merge request changes view, executing whenever other users navigate to that specific view. The vulnerability operates under CWE-79 which categorizes cross-site scripting flaws as weaknesses in input validation and output encoding.
The operational impact of this vulnerability extends beyond simple data theft or session hijacking, as it enables attackers to perform a wide range of malicious activities within the compromised user's browser context. An attacker who successfully exploits this vulnerability could potentially read sensitive project information, modify merge request content, access confidential data, or even escalate privileges within the GitLab instance. The persistent nature of the vulnerability means that once the malicious payload is injected, it continues to execute for all users who view the affected merge request changes, making it particularly dangerous in collaborative development environments where multiple team members regularly review merge requests.
Organizations utilizing affected GitLab versions face significant risk exposure through this vulnerability, as it can be exploited to compromise entire development workflows and potentially lead to supply chain attacks. The attack vector requires minimal privileges since the vulnerability exists in the application's display logic rather than requiring administrative access or code execution capabilities. Security teams should prioritize immediate patching of affected systems, as the vulnerability's persistence mechanism ensures that malicious payloads remain active until the affected merge requests are manually cleaned or the application is updated. The remediation strategy should include comprehensive review of existing merge requests for potential malicious content and implementation of additional monitoring for suspicious activities within the merge request functionality.
This vulnerability aligns with several tactics, techniques, and procedures documented in the MITRE ATT&CK framework, particularly under the T1059.007 technique for script injection and T1566 for credential access through social engineering. The persistent nature of the XSS payload makes it particularly effective for maintaining long-term access to compromised systems, while the integration with GitLab's core development workflow provides attackers with access to sensitive source code repositories and development artifacts. Organizations should implement additional security controls including web application firewalls, regular security scanning of merge request content, and user education regarding the dangers of viewing untrusted merge request changes from unknown sources. The vulnerability demonstrates the critical importance of input validation and output encoding in web applications, particularly those handling collaborative development workflows where user-generated content is displayed to multiple parties.