I try to mark content from a web-page (with pictures, hyperlinks etc) to clipboard and then paste it into Microsoft Word (belonging to the Office 365 Home suite).
Then I discover problems starting with the following warning:

"A potential vulnerability has been identified in Microsoft Office.

This document contains fields that can share data with external files
and Web sites. It is important that this file comes from a reliable
source."

(I do not use English as my working language, and this warning is translated to English using Google Translate... :-))

The screen is often flickering two or three times before the content is displayed.

In Office 2007/2010 it was possible to avoid this message by going to the Trust Center Setttings and under Privacy Options, select or clear "Check Microsoft Office documents that are from or link to suspicious Web sites" check box. But I do not find this check box in Office 365. :-(

What can I do to avoid this message ?

As to the flickering I recall that happening in all Office versions since about 1997. Microsoft apparently does not work on making their Office product operate smoothly (at least not on Windows.)

As a test I pasted web content into LibreOffice and it just worked without the warning messages. So it does indeed look like a choice made by Microsoft to hold hands and warn against every possible exploit or user error.

Turning off warnings like this has fallen out of favor in security circles as it removes a possible warning to the users. Microsoft is constantly beat up about security so they may have removed the off switch. As it appears to still paste but with the warning you may get no where with Microsoft. The usual reply is "works as designed."