CVE-2012-5491: z3c.form Default Form Field Values Disclosure in Plone
Summary
CVE-2012-5491: Plone Information Disclosure. Affects plone across 2 version ranges.
< 4.2.3
>= 4.3a0, < 4.3b1
Fixed in 4.2.3 or 4.3b1, depending on the release line you run. How to fix ↓
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Background
Plone is a content management system (CMS) built on top of the Zope application server. It provides an easy-to-use interface for creating and managing websites. z3c.form is a library used in Plone for building forms. It allows developers to define form fields and handle form submissions. However, prior to version 4.2.3 and 4.3 beta 1, Plone was vulnerable to an information disclosure issue in z3c.form. This vulnerability allowed remote attackers to obtain the default values of form fields by exploiting knowledge of the form location and the element ID.
Vulnerability Detail
The vulnerability in z3c.form allowed attackers to retrieve default form field values by leveraging specific knowledge about the form's location and the element ID. This information disclosure could potentially expose sensitive data or allow attackers to gain insights into the system's configuration. The impact of this vulnerability depends on the nature of the data exposed and the context in which the form is used. It is important to note that this vulnerability only affects Plone versions prior to 4.2.3 and 4.3 beta 1.
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 versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 4.2.34.2.3pip install --upgrade "plone==4.2.3" -
>= 4.3a0, < 4.3b14.3b1pip install --upgrade "plone==4.3b1"
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
If upgrading to a patched version is not immediately feasible, a temporary workaround can be implemented by modifying the affected forms to remove any sensitive default values. This can be achieved by explicitly setting the default values to empty or non-sensitive values. For example, if a form field has a default value of 'password123', it can be changed to an empty string or a generic value like 'N/A'. However, this workaround should be considered temporary, and upgrading to a patched version is still the recommended solution.
Conclusion
The vulnerability in z3c.form allowed remote attackers to obtain default form field values in Plone. To mitigate this issue, it is crucial to upgrade to a patched version of Plone (4.2.3 or later, or 4.3 beta 1 or later). If immediate upgrading is not feasible, a temporary workaround can be implemented by removing sensitive default values from affected forms. For further assistance or support in vulnerability remediation, please contact DevNack.com.
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FAQ
z3c.form is a library used in Plone for building forms. It provides a convenient way to define form fields and handle form submissions.
The vulnerability allows remote attackers to obtain the default values of form fields by exploiting knowledge of the form location and the element ID. This can potentially expose sensitive data or provide insights into the system's configuration.
The vulnerability affects Plone versions prior to 4.2.3 and 4.3 beta 1. It has been addressed in later versions, so upgrading to a patched release is recommended.
The disclosure of default form field values can expose sensitive information or provide attackers with insights into the system's configuration. The impact depends on the nature of the exposed data and the context in which the form is used.
To fix this vulnerability, it is recommended to upgrade to Plone version 4.2.3 or later, or version 4.3 beta 1 or later. These versions include the necessary patches to address the information disclosure issue in z3c.form.
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