CVE-2016-7136 in Plone
Summary
by MITRE
z3c.form in Plone CMS 5.x through 5.0.6 and 4.x through 4.3.11 allows remote attackers to conduct cross-site scripting (XSS) attacks via a crafted GET request.
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Analysis
by VulDB Data Team • 09/26/2022
The vulnerability identified as CVE-2016-7136 represents a critical cross-site scripting flaw within the z3c.form component of Plone CMS versions 4.x through 4.3.11 and 5.x through 5.0.6. This issue stems from insufficient input validation and output encoding mechanisms within the form processing framework that powers numerous Plone-based web applications. The vulnerability manifests when the application fails to properly sanitize user-supplied data that is subsequently rendered in web responses, creating an avenue for malicious actors to inject arbitrary JavaScript code into web pages viewed by other users. The flaw specifically affects GET requests, making it particularly dangerous as attackers can craft malicious URLs that, when clicked by unsuspecting users, execute harmful scripts within the victim's browser context. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a fundamental web application security weakness that has been consistently ranked among the top ten web application security risks by the OWASP Top Ten project. The ATT&CK framework categorizes this as a code injection technique under the T1566.001 sub-technique, specifically targeting web application input validation mechanisms.
The technical exploitation of this vulnerability requires minimal prerequisites and can be accomplished through simple URL manipulation techniques. Attackers can craft malicious GET parameters containing script payloads that bypass the application's sanitization filters, leading to the execution of arbitrary JavaScript code in the context of the victim's browser session. The impact extends beyond simple script execution as it can enable session hijacking, credential theft, and redirection to malicious sites. When combined with other vulnerabilities or social engineering techniques, this XSS flaw can facilitate more sophisticated attacks such as CSRF (Cross-Site Request Forgery) or privilege escalation within the application's user management system. The vulnerability affects the core form rendering functionality of Plone, which is extensively used across numerous websites and web applications, amplifying the potential attack surface significantly.
The operational impact of this vulnerability is substantial for organizations relying on Plone CMS, as it can compromise the integrity and confidentiality of user data. Successful exploitation can lead to unauthorized access to user sessions, enabling attackers to perform actions on behalf of legitimate users, including modifying content, accessing sensitive information, or even escalating privileges within the application. The vulnerability's presence in both major version branches of Plone (4.x and 5.x) indicates a widespread exposure across numerous production environments, making it particularly concerning for security teams managing multiple Plone installations. Organizations utilizing Plone for content management, intranet solutions, or public websites face significant risk, as the vulnerability can be exploited through simple web browsing activities without requiring complex attack vectors or specialized tools. Security monitoring systems should be configured to detect suspicious GET parameters and unusual request patterns that may indicate attempts to exploit this vulnerability.
Mitigation strategies for CVE-2016-7136 primarily involve immediate application of available security patches and updates from the Plone development team. Organizations should upgrade to patched versions of Plone CMS that address the input validation and output encoding deficiencies within the z3c.form component. Additionally, implementing proper input sanitization and output encoding practices at the application level can provide defense-in-depth measures. Web Application Firewalls should be configured to filter and block suspicious GET parameters containing known XSS payload patterns. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities within the application stack. The implementation of Content Security Policy headers can provide additional protection against script execution, though this should not be considered a complete solution. Organizations should also establish proper security monitoring and incident response procedures to detect and respond to exploitation attempts. Given the nature of this vulnerability, regular security awareness training for developers and administrators is crucial to prevent similar issues in custom application code that interfaces with the Plone CMS framework.