Medium severity · published Dec 5, 2025
CVE-2025-66548
Nextcloud Deck app allows to spoof file extensions by using RTLO characters
5.5
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 4% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SE
security-advisories · nextcloud
>= 1.15.0-beta.1, < 1.15.1; >= 1.14.0-beta.1, < 1.14.4; < 1.12.7 · source: vendor
DE
Deck · Nextcloud
before 1.12.7; 1.14.0 before 1.14.4; 1.15.0 before 1.15.1 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66548
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66548
Patch
https://github.com/nextcloud/deck/commit/afa95d3c507465b9d31af7c88c69b76711ef185a
Issue Tracking
https://github.com/nextcloud/deck/pull/6671
Patch
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-xjvq-xvr7-xpg6
Permissions Required
https://hackerone.com/reports/2326618
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