A Microsoft file hosting and synchronization service.
This seems to be resolved for me too, after having lost my shared folders to Internet Shortcuts back in April 2025 (I know that others have been affected for much longer).
Yesterday, my OneDrive said it was processing some change for several hours, then proceeded to download several hundred gigabytes of files. This morning I noticed that my shared folders that had previously been Internet Shortcuts had been renamed, and the old shared folders reappearing as proper folders like they had been before.
Hopefully this fix will propagate to everyone else in good time.