Microsoft Edge 90.0.818.49 fixes various bugs and performance issues. This is all the information Microsoft has given about this update.
It would make sense that not much has changed in this update since it has been a very short time since the latest update which was known to bring quite a few fixes to significant vulnerabilities.
You can download this update directly (links below) or you can update over the air from the Edge browser itself. To check if your browser needs updating to the latest version, you can open Edge and head to Settings and more > Settings > About Microsoft Edge.
You can read more about the release notes here: Release notes for Microsoft Edge Stable Channel
Download (Microsoft Edge Build 90.0.818.49)
- Microsoft Edge-Stable Channel Version 90 Update for x64 based Editions (Build 90.0.818.49)
- Microsoft Edge-Stable Channel Version 90 Update for ARM64 based Editions (Build 90.0.818.49)