Nextcloud Deck file extension spoofing via RTLO (before 1.12.7/1.14.4/1.15.1)
CVE-2025-66548 Published on December 5, 2025
Nextcloud Deck app allows to spoof file extensions by using RTLO characters
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.
Vulnerability Analysis
CVE-2025-66548 is exploitable with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, with no impact on integrity, and no impact on availability.
Weakness Type
What is an Output Sanitization Vulnerability?
The software 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.
CVE-2025-66548 has been classified to as an Output Sanitization vulnerability or weakness.
Products Associated with CVE-2025-66548
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Affected Versions
nextcloud security-advisories:- Version >= 1.15.0-beta.1, < 1.15.1 is affected.
- Version >= 1.14.0-beta.1, < 1.14.4 is affected.
- Version < 1.12.7 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.