Authentication prompts when opening a document

[Surreptitious]

Our users have started receiving proxy authentication prompts when opening Excel/Word/Etc and selecting File/Open.  The domains to which it wants to connect are:

storage.googleapis.com

cdn01.boxcdn.net

I could create an authentication bypass, but I not wish to as I have no idea why Office should need to connect to either.  I have deselected 'Optional connected experiences' but the prompts remain.

Does anyone know why O365 is attempting to use these domains, or is it simply additional office content being fetched?  Is there a way to disable the connections within O365?

Thank you in advance.

[#2]

@Surreptitious we are having the same issue, only began this week. Expect triggered by an Office update? Again would like to get confirmation on cause. Believe it is related to O365 integrations.

[#3]

@Surreptitious 

Hello 
Same here. Any solutions.

Best Regards
Maik

[#4]

Signing out and in O365 did help

[#5]

The attempts to access the two domains do not present a user agent; I was forced to bypass authentication for them on our proxy, and then implement a block for the same domains.

Still, this should not be happening.

[#6]

Our organization has had 3 users experience this so far. They have all had various office 2019 documents open (Excel or Word) and are all running this version (16.0.10386.20017).

None have specified that they were opening a document and it occurred. The most recent had a document open for a long time during the day and it began to pop-up.

As a possible fix, we have turned off the Optional connected experiences and the "Let office connect to online services from Microsoft..." in the Trust Center - Privacy Options dialogue.

[#7]

We turned that off but unfortunately it didn't resolve the issue.

[#8]

Any update on this? Over the last few weeks had a few users now reporting this... Any explanation or fix for this? Thanks