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Stored XSS in Gallery application (NC-SA-2017-010)

8th May 2017

Risk level: Low

CVSS v3 Base Score: 3 (AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:N/A:N)

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

HackerOne report: 222838


A JavaScript library used by Nextcloud for sanitizing untrusted user-input suffered from a XSS vulnerability caused by a behaviour change in Safari 10.1 and 10.2.Note that Nextcloud employs a strict Content-Security-Policy preventing exploitation of this XSS issue on modern web browsers.

Affected Software

  • Nextcloud Server < 11.0.3 (CVE-2017-0893)
  • Nextcloud Server < 10.0.5 (CVE-2017-0893)
  • Nextcloud Server < 9.0.58 (CVE-2017-0893)

Action Taken

The vulnerable library has been updated.


It is recommended that all instances are upgraded to Nextcloud 9.0.58, 10.0.5 or 11.0.3.


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

  • Lukas Reschke - Nextcloud GmbH ( - Vulnerability discovery and disclosure.

This advisory is licensed CC BY-SA 4.0.

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