ownCloud Server before 5.0.19, 6.x before 6.0.7, and 7.x before 7.0.5 allows remote authenticated users to bypass the file blacklist and upload arbitrary files via a file path with UTF-8 encoding, as demonstrated by uploading a .htaccess file.
https://owncloud.org/security/advisory/?id=oc-sa-2015-004
https://owncloud.org/security/advisory/?id=oc-sa-2015-003