Bug 2506849

Summary: CVE-2026-66010 nextcloud: DOMPurify: Cross-Site Scripting (XSS) via custom element attribute bypass [fedora-all]
Product: [Fedora] Fedora Reporter: Ganesh <gnaik>
Component: nextcloudAssignee: Andrew Bauer <zonexpertconsulting>
Status: ON_QA --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: 45CC: pampelmuse, zonexpertconsulting
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["6b1db381-899f-4e90-84fe-976062325d58"]}
Fixed In Version: Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2506731    

Description Ganesh 2026-07-24 16:55:34 UTC
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

Comment 1 Fedora Update System 2026-08-16 21:15:08 UTC
FEDORA-EPEL-2026-b2421df34a (nextcloud-34.0.3-1.el10_3) has been submitted as an update to Fedora EPEL 10.3.
https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2026-b2421df34a

Comment 2 Fedora Update System 2026-08-16 21:16:53 UTC
FEDORA-2026-a1368a72b4 (nextcloud-34.0.3-1.fc44) has been submitted as an update to Fedora 44.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-a1368a72b4

Comment 3 Fedora Update System 2026-08-16 21:17:26 UTC
FEDORA-2026-625cbe86c8 (nextcloud-34.0.3-1.fc43) has been submitted as an update to Fedora 43.
https://bodhi.fedoraproject.org/updates/FEDORA-2026-625cbe86c8

Comment 4 Fedora Update System 2026-08-16 21:21:41 UTC
FEDORA-EPEL-2026-15025fbfe6 (nextcloud-34.0.3-1.el10_2) has been submitted as an update to Fedora EPEL 10.2.
https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2026-15025fbfe6

Comment 5 Fedora Update System 2026-08-17 01:17:15 UTC
FEDORA-EPEL-2026-15025fbfe6 has been pushed to the Fedora EPEL 10.2 testing repository.

You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2026-15025fbfe6

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 6 Fedora Update System 2026-08-17 01:31:07 UTC
FEDORA-2026-a1368a72b4 has been pushed to the Fedora 44 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-a1368a72b4`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-a1368a72b4

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 7 Fedora Update System 2026-08-17 01:33:13 UTC
FEDORA-EPEL-2026-b2421df34a has been pushed to the Fedora EPEL 10.3 testing repository.

You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2026-b2421df34a

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 8 Fedora Update System 2026-08-17 01:50:23 UTC
FEDORA-2026-625cbe86c8 has been pushed to the Fedora 43 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-625cbe86c8`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-625cbe86c8

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 9 Aoife Moloney 2026-08-17 15:36:36 UTC
This bug appears to have been reported against 'rawhide' during the Fedora Linux 45 development cycle.
Changing version to 45.