CVE-2011-4764 in Plesk Small Business Panel
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in the Site Editor (aka SiteBuilder) feature in Parallels Plesk Small Business Panel 10.2.0 allow remote attackers to inject arbitrary web script or HTML via crafted input to a PHP script, as demonstrated by Wizard/Edit/Modules/Image and certain other files.
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Analysis
by VulDB Data Team • 01/12/2018
The vulnerability identified as CVE-2011-4764 represents a critical cross-site scripting weakness within the Site Editor component of Parallels Plesk Small Business Panel version 10.2.0. This flaw resides in the web application's input validation mechanisms, specifically affecting the SiteBuilder feature that enables users to create and modify website content through an interactive interface. The vulnerability manifests when the application fails to properly sanitize user-supplied data before incorporating it into dynamic web pages, creating opportunities for malicious actors to execute arbitrary scripts within the context of other users' browsers.
The technical implementation of this vulnerability stems from insufficient output encoding and input validation within multiple PHP scripts, particularly those located in the Wizard/Edit/Modules/Image directory and similar components. Attackers can exploit this weakness by crafting malicious payloads that contain JavaScript code or HTML elements and submitting them through the affected input fields. When the application processes these inputs without proper sanitization, the malicious content gets stored and subsequently executed whenever other users view the affected pages. This creates a persistent XSS vector that can be leveraged to steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users.
The operational impact of this vulnerability extends beyond simple data theft, as it fundamentally compromises the integrity and security of the entire Plesk panel environment. Remote attackers can leverage the XSS flaw to establish persistent access to compromised accounts, potentially escalating privileges or gaining unauthorized access to customer websites and data. The vulnerability affects the core administrative functionality of the platform, making it particularly dangerous for hosting providers who rely on Plesk for managing multiple client accounts. From an attack perspective, this vulnerability aligns with ATT&CK technique T1566.001 for initial access through malicious web content, and T1059.001 for command and control through script injection.
Security professionals should note that this vulnerability demonstrates poor input validation practices that violate established security principles and aligns with CWE-79 which describes Cross-Site Scripting flaws. The weakness exists in the application's failure to implement proper content security policies and output encoding mechanisms, creating a persistent threat that can affect any user who views compromised content. Organizations running Plesk Small Business Panel 10.2.0 should immediately implement mitigations including input sanitization, output encoding, and application-level protections such as Content Security Policy headers. Additionally, regular security updates and patches should be prioritized, as this vulnerability represents a known weakness that has been addressed in subsequent versions of the software. The incident highlights the critical importance of proper input validation in web applications and demonstrates how seemingly minor security oversights can create significant operational risks for hosting providers and their customers.