After you install the December 2022 or January 2023 security updates for SharePoint Server, you might not be able to browse to a SharePoint website if the site URL ends in a string that matches a blocked file type extension for that web application. When you browse to such a site, you might receive the following error message:
The URL '/sitename' is invalid. It may refer to a nonexistent file or folder, or refer to a valid file or folder that is not in the current Web.
Microsoft is researching this issue and will update this article when a fix is available.
To work around this issue, add a forward slash to the end of the site URL when you browse to the site. For example, browse to https://server/sites/sitename/ instead of https://server/sites/sitename.