CVE-2018-20876 in cPanel
Summary
by MITRE
cPanel before 74.0.8 allows self XSS in the Site Software Moderation interface (SEC-434).
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Analysis
by VulDB Data Team • 07/17/2020
The vulnerability CVE-2018-20876 represents a self cross-site scripting flaw discovered in cPanel versions prior to 74.0.8 within the Site Software Moderation interface. This security weakness falls under the category of CWE-79 - Cross-site Scripting, specifically classified as self-XSS since the malicious payload is executed within the context of the authenticated user's session rather than being injected into the application's response. The vulnerability manifests in the Site Software Moderation functionality where administrators can manage and moderate website software installations and configurations.
The technical implementation of this flaw occurs when the application fails to properly sanitize or escape user-controllable input data within the moderation interface. When administrators interact with the Site Software Moderation component, the application stores and displays user-provided content without adequate input validation or output encoding mechanisms. This creates an environment where malicious actors can inject malicious script code into fields that are subsequently rendered back to the administrator's browser session, enabling the execution of arbitrary JavaScript code within the context of the victim's authenticated session.
The operational impact of this vulnerability is significant as it allows attackers to leverage the privileges of authenticated administrators within the cPanel environment. An attacker who gains access to an administrator account could exploit this vulnerability to perform actions such as stealing session cookies, modifying website configurations, installing malicious software, or accessing sensitive system information. The self-XSS nature means that the attack requires the administrator to be tricked into clicking on a malicious link or interacting with the compromised interface, but once executed, the payload can operate with the full privileges of the administrator account.
This vulnerability directly relates to ATT&CK technique T1059.007 - Command and Scripting Interpreter: JavaScript, where attackers can execute malicious JavaScript code within the context of the victim's browser session. The attack vector typically involves social engineering tactics to convince administrators to interact with maliciously crafted content within the cPanel interface. The mitigation strategy involves applying the vendor-provided security patch that addresses the input sanitization and output encoding deficiencies in the Site Software Moderation interface. Organizations should also implement additional security measures such as regular security updates, input validation, and output encoding practices to prevent similar vulnerabilities from occurring in other components of the system.
The vulnerability demonstrates a critical weakness in the application's security architecture where proper input validation and output encoding mechanisms were not implemented consistently across all user-controllable data entry points. This represents a common security oversight where developers assume that certain administrative interfaces are less vulnerable to XSS attacks, leading to inadequate security controls. The remediation process requires not only patching the specific vulnerability but also conducting comprehensive security reviews of the application's input handling and output rendering mechanisms to ensure that similar flaws do not exist in other parts of the system. The incident highlights the importance of implementing defense-in-depth strategies that include multiple layers of security controls to protect against various attack vectors including those that exploit user interaction with web interfaces.