Joomla 3.8.10 is now available. This is a bug fix release addressing one bug introduced into 3.8.9 which affects Windows servers.
What's in 3.8.10?
Joomla 3.8.10 is addressing one bug introduced into Joomla 3.8.9. This release is fixing the autoloader for Windows platforms.
If you are using a Windows platform, please update your site to 3.8.10 as soon as possible.