The December release of the ArcGIS Security Advisor v2.7.3 retired the HTTP Check Module.
This module had been available for both ArcGIS Online and Enterprise to help migrate item content in preparation of December of 2020 when ArcGIS Online would be enforcing HTTPS only references.
The October 29th release of the Security Advisor removed the HTTP Check module from the ArcGIS Online login accounts. Customers using ArcGIS Enterprise login still had the HTTP Check module available until the end December 2021.
Remember that the best way to access and use the Security Advisor is from the ArcGIS Trust Center.
If you have any questions visit the ArcGIS Trust Center where we have security and privacy information. If your not able to find what you are looking for, please reach out to the Software Security & Privacy Team at firstname.lastname@example.org
– Esri Software Security & Privacy Team