CVE-2025-66554
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-12-05

Last updated on: 2025-12-09

Assigner: GitHub, Inc.

Description
Contacts app for Nextcloud easily syncs contacts from various devices with your Nextcloud and allows editing. Prior to 5.5.4, 6.0.6, and 7.2.5, a malicious user was able to modify their organisation and title field to load additional CSS files. Javascript and other options were correctly blocked by the content security policy of the Nextcloud Server code. This vulnerability is fixed in 5.5.4, 6.0.6, and 7.2.5.
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Meta Information
Published
2025-12-05
Last Modified
2025-12-09
Generated
2026-06-16
AI Q&A
2025-12-05
EPSS Evaluated
2026-06-15
NVD
CVE-2025-66554
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
nextcloud contacts From 5.0.0 (inc) to 5.5.4 (exc)
nextcloud contacts From 6.0.0 (inc) to 6.0.6 (exc)
nextcloud contacts From 7.0.0 (inc) to 7.2.5 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
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Executive Summary

This vulnerability in the Nextcloud Contacts app allowed a malicious user to modify their organisation and title fields to load additional CSS files. Although Javascript and other potentially harmful content were blocked by the Nextcloud Server's content security policy, the ability to load extra CSS could be exploited. The issue was fixed in versions 5.5.4, 6.0.6, and 7.2.5 of the app.

Impact Analysis

The vulnerability could allow a malicious user to alter the appearance or styling of the Contacts app interface by loading additional CSS files, potentially leading to misleading or confusing user interfaces. However, it does not allow execution of Javascript or direct data compromise. The impact is limited to integrity (modification) of the interface, with no confidentiality or availability impact.

Mitigation Strategies

Update the Nextcloud Contacts app to version 5.5.4, 6.0.6, or 7.2.5 or later, as these versions contain the fix for this vulnerability.

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