Nextcloud Deck up to 1.12.6/1.14.3/1.15.0 File Extension escape output

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Nextcloud Deck up to 1.12.6/1.14.3/1.15.0. This affects an unknown part of the component File Extension Handler. Performing a manipulation results in escape output. This vulnerability is known as CVE-2025-66548. Attacking locally is a requirement. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Nextcloud Deck up to 1.12.6/1.14.3/1.15.0. It has been classified as problematic. This affects an unknown functionality of the component File Extension Handler. The manipulation with an unknown input leads to a escape output vulnerability. CWE is classifying the issue as CWE-116. The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved. This is going to have an impact on integrity. The summary by CVE is:

Nextcloud Deck is a kanban style organization tool aimed at personal planning and project organization for teams integrated with Nextcloud. Prior to 1.12.7, 1.14.4, and 1.15.1, file extension can be spoofed by using RTLO characters, tricking users into download files with a different extension than what is displayed. This vulnerability is fixed in 1.12.7, 1.14.4, and 1.15.1.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2025-66548 since 12/04/2025. The exploitability is told to be easy. An attack has to be approached locally. Neither technical details nor an exploit are publicly available.

Upgrading to version 1.12.7, 1.14.4 or 1.15.1 eliminates this vulnerability. Applying the patch afa95d3c507465b9d31af7c88c69b76711ef185a is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Cloud Software

Vendor

• Nextcloud

Name

• Deck

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.12.0
• 1.12.1
• 1.12.2
• 1.12.3
• 1.12.4
• 1.12.5
• 1.12.6
• 1.13
• 1.14
• 1.14.0
• 1.14.1
• 1.14.2
• 1.14.3
• 1.15.0

License

• open-source

Website

• Product: https://github.com/nextcloud/deck/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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