Otherwise, in the 95 era, I believe you'd likely be finding out through a software vendor or otherwise that a certain fixpack from Microsoft might fix an issue and you should go grab an update then.
Oofda. That can't have been an accident.
https://en.m.wikipedia.org/wiki/Windows_Update#Critical_Upda...
Anything else would have been a direct fix package - such as the DCOM95 OLE Update, DUN 1.4, or Winsock 2 -- things that you only installed if you needed something that used those functions, and often would become bundled with the software anyways because users might not have been given those updates out of the box.
There was at least one XP-era update CD that I do recall - the Windows Security Update 2004 contained patches for 98 through XP and was available by mail from Microsoft.
"Critical Update Notification Utility (initially Critical Update Notification Tool) is a background process that checks the Windows Update web site on a regular schedule for new updates that have been marked as "Critical". It was released shortly after Windows 98."
Unfortunately, the citation for that is no longer active on MS's site, and the archive.org version no longer works either.