Nexcloud desktop is the Desktop sync client for Nextcloud. An attacker can inject arbitrary HyperText Markup Language into the Desktop Client application in the notifications. It is recommended that the Nextcloud Desktop client is upgraded to 3.6.1. There are no known workarounds for this issue.
Nextcloud also ships a CLI utility called nextcloudcmd which is sometimes used for automated scripting and headless servers. Versions of nextcloudcmd prior to 3.6.1 would incorrectly trust invalid TLS certificates, which may enable a Man-in-the-middle attack that exposes sensitive data or credentials to a network attacker. This affects the CLI only. It does not affect the standard GUI desktop Nextcloud clients, and it does not affect the Nextcloud server.