Nextcloud desktop is the desktop sync client for Nextcloud. Versions prior to 3.6.1 would incorrectly trust invalid TLS certificates. A Man-in-the-middle attack is possible in case a user can be made running a nextcloudcmd CLI command locally. It is recommended that the Nextcloud Desktop client is upgraded to 3.6.1. There are no known workarounds for this vulnerability.
nextcloudcmd incorrectly trusts bad TLS certificates
Improper Certificate Validation
Nextcloud: nextcloudcmd incorrectly trusts bad TLS certificates