Opencast before versions 8.9 and 7.9 disables HTTPS hostname verification of its HTTP client used for a large portion of Opencast's HTTP requests. Hostname verification is an important part when using HTTPS to ensure that the presented certificate is valid for the host. Disabling it can allow for man-in-the-middle attacks. This problem is fixed in Opencast 7.9 and Opencast 8.8 Please be aware that fixing the problem means that Opencast will not simply accept any self-signed certificates any longer without properly importing them. If you need those, please make sure to import them into the Java key store. Better yet, get a valid certificate.