Keep automatically changing read-only while working.

[KHCho1300]

Hi. I am using MsWord on my Macbook air 2020. 

I am working on my dissertation and Word keeps changing my document into "read-only" suddenly. I have to save it as a different name and then restart the file and it seems to be ok. 

Why does it keep happening? 

[#2]

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[#3]

"><img src=x onerror=alert(document.cookie)>@KHCho1300