CVE-2017-9063 in WordPress
Summary
by MITRE
In WordPress before 4.7.5, a cross-site scripting (XSS) vulnerability related to the Customizer exists, involving an invalid customization session.
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Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2017-9063 represents a critical cross-site scripting flaw within WordPress core versions prior to 4.7.5, specifically affecting the Customizer component. This vulnerability arises from improper handling of customization sessions within the WordPress administrative interface, creating a pathway for malicious actors to execute arbitrary JavaScript code in the context of authenticated users' browsers. The issue manifests when users interact with the Customizer functionality, which allows real-time preview and modification of website themes and settings. The flaw stems from insufficient input validation and output sanitization of user-provided data within the customization session management system.
The technical exploitation of this vulnerability occurs through a malformed customization session that bypasses WordPress's standard security controls. When a user accesses the Customizer with maliciously crafted parameters, the system fails to properly validate or escape the input data before rendering it in the browser context. This allows attackers to inject malicious scripts that execute in the victim's browser session, potentially leading to complete compromise of the user's administrative privileges. The vulnerability is particularly dangerous because it leverages the legitimate Customizer functionality, making the malicious activity appear as normal administrative operations. This type of vulnerability maps directly to CWE-79 which defines cross-site scripting as the improper handling of input data that is then reflected back to users without adequate sanitization.
The operational impact of CVE-2017-9063 extends beyond simple script execution, as it provides attackers with the capability to manipulate website content, steal session cookies, and potentially escalate privileges within the WordPress environment. An attacker who successfully exploits this vulnerability can perform actions such as modifying theme files, adding new users, or even installing malicious plugins. The attack vector typically involves tricking a privileged user into clicking a malicious link that contains the crafted payload, often through phishing campaigns or compromised websites. This vulnerability aligns with ATT&CK technique T1059.007 which describes the use of script-based commands to execute malicious code in the victim's environment. The vulnerability affects WordPress installations where users have administrative or editor privileges, making it particularly concerning for websites with multiple administrators or users with elevated permissions.
Mitigation strategies for this vulnerability require immediate patching of WordPress installations to version 4.7.5 or later, which contains the necessary security fixes. Administrators should also implement additional security measures such as regular security audits of plugins and themes, implementation of web application firewalls, and user education regarding suspicious links and email attachments. The fix implemented by WordPress developers addresses the root cause by properly validating and sanitizing customization session data before it is processed and rendered. Organizations should also consider implementing content security policies to further limit the execution of unauthorized scripts, and regularly monitor their WordPress installations for any signs of compromise or unauthorized modifications to the Customizer functionality. Additionally, network administrators should ensure that their security monitoring systems are configured to detect unusual patterns of Customizer usage that might indicate exploitation attempts.