Symptoms:

• After Updating to vSphere 6.7 Update 1, Update Manager gives Response with status: 401 OK for URL at random occasions when used with FireFox browser
• Complete Error Message on the GUI for host scan task is similar to:
  
  Response with status: 401 OK for URL: https://<FQDN of VUM server>ui/vum-ui/rest/vcobjects/urn:vmomi:HostSystem:host-10:478c8cfc-c88e-4fdb-9e1a-93d899697bf7/isUpdateSupported
  
  Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.

VMware vCenter Server 7.0.0
VMware vCenter Server 7.0.1

This is an expected behavior from a session validation security feature against an expired session from browser cache.

This issue is resolved in VMware vCenter 6.7 Update 2, available at VMware Downloads.

Workaround:
To workaround this issue, use another browser or clear/disable browser cache on Firefox and retry:

• Please refer to respective browser documentation to clear the cache:
  • How to clear the Firefox cache
  • How do I stop Firefox from caching pages?

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