Issue Description

By default Nextcloud Mail will not load images in HTML mail. This could be bypassed with // uri.

Affected versions

Nextcloud Mail Application up to 1.10.3

Details

Creating image tag with following syntax <img src=//server/trackingpixel.png> will bypass the image blocking filter.

Fix

Vendor notified 17.08.2021
Fix released 15.09.2021

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-6q9v-wm8r-rcv5

CVE-2021-39220 was issued

https://cve.mitre.org/cgi-bin/cvename.cgi?name=2021-39220