Below is the change log for testing releases. For stable releases see Release history. For recent changes in the develop-branch please refer to git commit history.
NOTE: The issue with the expired certificate may prevent NZBGet from doing update check and performing the update itself via web interface. The solution is to temporary disable certificate check via option Settings->Security-CertCheck and reenable it after update. This is safe because the downloaded package is verified for authenticity during update routine (even though the communication channel may be not safe).
Alternatively you can of course download and install NZBGet manually using manuals on NZBGet download page at https://nzbget.net/download.
For older (stable) releases see Release history.