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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2025-12-05

Last Modified

2025-12-09

Generated

2026-07-06

AI Q&A

2025-12-05

EPSS Evaluated

2026-07-05

NVD

CVE-2025-66554

Affected Vendors & Products

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

KEV

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.

Attack-Flow Graph

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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