Where should this be reported?
Either the checksum for ArcGIS-1081-S-UN2-PatchB.msp appears to be wrong, or the patch file is corrupt or compromised. I cannot validate the file against any published hash.
On the patch download page it is (MD5): 455ADECD1A49032B9AA338BE96173E18
In the patch notification file it is (MD5): 4DB7CA835962E6C2BFA85A7786FDE547 (this appears to be for the ArcGIS-1081-S-UN2-Patch.msp file (without the "B").
The value I calculate is: (MD5) B4B20C8491FC4EBF2AF612928B70391D
There are a number of other patches in the patch notification file that have missing or incorrect checksums: e.g.
ArcGIS-1071-DT-FGSP-Patch.msp (missing)
ArcGIS-109-PFA-MM1-Patch.msp (has an (extra) leading 1 in the hash)
ArcGIS-1071-S-FGSP-Patch.msp (missing)
ArcGIS-1081-S-PS-Patch.msp (missing)
ArcGIS-1081-S-IS-Patch.msp (has an SHA256 and MD5 hash in the SHA256sums list and an incorrect MD5 hash in the MD5sums list)
ArcGIS-1081-S-PSTE-Patch.msp (has an incorrect SHA256 hash)
ArcGIS-1081-WAI-S-Patch.msp (missing)
ArcGISDataReviewerServer1081Patch1.msp (missing)
ArcGISDataReviewerServer1081Patch2.msp (missing)