CVE-2021-32728

The Nextcloud Desktop Client is a tool to synchronize files from Nextcloud
Server with a computer. Clients using the Nextcloud end-to-end encryption
feature download the public and private key via an API endpoint. In
versions prior to 3.3.0, the Nextcloud Desktop client fails to check if a
private key belongs to previously downloaded public certificate. If the
Nextcloud instance serves a malicious public key, the data would be
encrypted for this key and thus could be accessible to a malicious actor.
This issue is fixed in Nextcloud Desktop Client version 3.3.0. There are no
known workarounds aside from upgrading.