When adding a custom SSL certificate and key to a website, we checked its syntax only by now. If an invalid certificate or key was configured, or a certificate did not match the added key, the configuration was saved. Even if this change was not applied to the server due to the broken configuration, we encountered a case where this led to the web server not being available anymore.
To prevent possible similar problems, we now fully validate each SSL certificate and key, and also compare their fingerprints to make sure they are matching each other.
You still have to manually include and check potential intermediate certificates, as outlined here. If you are not proficient with this topic, we are happy to guide you through the process and will also order and install custom certificates on your behalf.
Reference: #1032