ownCloud Desktop Client before 1.8.2 does not call QNetworkReply::ignoreSslErrors with the list of errors to be ignored, which allows man-in-the-middle attackers to bypass the user's certificate distrust decision and obtain sensitive information by leveraging a self-signed certificate and a connection to a server using its own self-signed certificate.
https://owncloud.org/security/advisory/?id=oc-sa-2015-009
https://github.com/owncloud/client/issues/3283