CVE-2021-33507: Reflected XSS in Zope Products.CMFCore and Products.PluggableAuthService
Summary
CVE-2021-33507: Zope Products.CMFCore before 2.5.1 and Products.PluggableAuthService before 2.6.2, as used in Plone through 5.2.4 and other products, allow Reflected XSS. Affects plone versions < 5.2.5. Fixed in 5.2.5. How to fix ↓
Also tracked for
- products-cmfcore · PyPI
- products-pluggableauthservice · PyPI
- products-cmfcore · PyPI
The same CVE-2021-33507 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Zope Products.CMFCore is a component of the Zope Content Management Framework (CMF) that provides core functionality for content management systems. Products.PluggableAuthService is a plugin-based authentication and authorization framework for Zope. These packages are widely used in various applications, including Plone. Plone is an open-source content management system built on top of Zope. The vulnerability allows for Reflected Cross-Site Scripting (XSS) attacks, which can lead to the execution of malicious scripts in the context of a user's browser.
Vulnerability Detail
The vulnerability arises from insufficient input sanitization in Zope Products.CMFCore and Products.PluggableAuthService. Attackers can exploit this by injecting malicious scripts into user-supplied input, such as URLs or form fields. When unsuspecting users interact with the affected application, the injected scripts are executed in their browsers, potentially leading to session hijacking, data theft, or other malicious activities. This vulnerability affects Plone versions up to 5.2.4 and other products that rely on these vulnerable packages.
How To Fix
Latest published version: 6.2.2 as of 23 Oct 2026
pip install --upgrade "plone==6.2.2"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
5.2.5
This is the first release that contains the fix.
pip install --upgrade "plone==5.2.5"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, developers can implement output encoding to prevent the execution of injected scripts. This can be achieved by using appropriate encoding functions or libraries, such as HTML escaping functions. By encoding user-supplied input before displaying it in HTML pages, the risk of XSS attacks can be mitigated. However, this should be considered a temporary solution, and upgrading to the fixed versions is strongly recommended.
Conclusion
In conclusion, the vulnerability in Zope Products.CMFCore and Products.PluggableAuthService allows for Reflected XSS attacks, posing a risk of executing malicious scripts in users' browsers. Upgrading to the fixed versions and implementing proper input validation and output encoding are crucial to mitigate this vulnerability. For further assistance or support in vulnerability remediation, please contact DevNack.com.
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FAQ
The vulnerability allows for Reflected XSS attacks, which can lead to the execution of malicious scripts in users' browsers. This can result in session hijacking, data theft, or other malicious activities.
Plone versions up to 5.2.4 are affected by this vulnerability.
At the time of this report, there are no known public exploits specifically targeting this vulnerability. However, it is important to promptly apply the recommended fixes to mitigate the risk.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability. Simply provide your Pipfile.lock file, and Vulert will analyze it for any open-source vulnerabilities, including this one.
You can find more information about this vulnerability, including the technical details and the fixed versions, in the advisory published on the PyPI advisory database. The source link is provided in the vulnerability details section.
References
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