What’s Vulnerable › Vulnerabilities

CVE-2025-66548: Nextcloud Deck app allows to spoof file extensions by using RTLO characters

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-12-05 · updated 2026-10-15
• Weakness: CWE-116

Description

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.

Affected products

• Nextcloud Deck: before 1.12.7; from 1.14.0 before 1.14.4; from 1.15.0 before 1.15.1 — fixed in 1.12.7, 1.14.4, 1.15.1

How to fix

Upgrade to a fixed version: Nextcloud Deck 1.12.7, 1.14.4, 1.15.1. Check the vendor advisory for mitigations.

References

• https://github.com/nextcloud/deck/commit/afa95d3c507465b9d31af7c88c69b76711ef185a
• https://github.com/nextcloud/deck/pull/6671
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-xjvq-xvr7-xpg6
• https://hackerone.com/reports/2326618

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