How to solve "Failed Signature verification", for downloads of ColdFusion updates--since Oct 2022
Update Jul 2023: Before considering what I share in this post, note that if you have updated your CF to use the Java update from Jul 2023, the cause of this error may be due to a totally different issue. See my post from July 2023 on that matter.
Update Feb 2023: In mid-February 2023, Adobe did re-sign their jars and placed them on the uploads site so that either the CF Admin update download or anyone performing a manual download after that date WOULD get the newly signed jars, and the problem below then no longer happens. (They are now signed as "SHA256withRSA, 4096-bit key".) I leave the rest here still for those who would want to understand what DID happen and why the update jars that were in place then DID change (slightly) for this reason.