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Reflected XSS in error pages (NC-SA-2017-008)

8th May 2017

Risk level: Low

CVSS v3 Base Score: 3.5 (AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N)

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

HackerOne report: 216812


Inadequate escaping of error messages leads to XSS vulnerabilities in multiple components.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-2017-0891)
  • Nextcloud Server < 10.0.5 (CVE-2017-0891)
  • Nextcloud Server < 9.0.58 (CVE-2017-0891)

Action Taken

Error messages are now properly escaped.


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:

This advisory is licensed CC BY-SA 4.0.

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