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Reflected XSS in Gallery application (NC-SA-2016-009)

10th October 2016

Risk level: Medium

CVSS v3 Base Score: 6.1 (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)

CWE: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (CWE-79)

HackerOne report: 165686


The gallery app was not properly sanitizing exception messages from the Nextcloud server. Due to an endpoint where an attacker could influence the error message this lead to a reflected Cross-Site-Scripting vulnerability.

Affected Software

Action Taken

Error messages are now properly sanitized.


It is recommended that all instances are upgraded to Nextcloud 10.0.1.


The Nextcloud team thanks the following people for their research and responsible disclosure of the above advisory:

  • Aliaksei Panamarenka - Vulnerability discovery and disclosure.

This advisory is licensed CC BY-SA 4.0.

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