We unfortunately had to pull this week's 4.0.8 and 4.0.9 releases, due to a packaging issue that broke the diff viewer.
Today's release of 4.0.10 is a replacement for these releases, and will restore working functionality.
This is our first time encountering such a rare breakage, but it's an interesting one, and we're evaluating how to avoid this in the future and to improve our automated testing.
Updating to Review Board 4.0.10
If you're on any prior release, including 4.0.9, you can upgrade as normal. Our official Docker images have also been updated for 4.0.10.
If you missed the 4.0.8 or 4.0.9 releases, we've included all of the improvements in the Review Board 4.0.10 release notes.