Something very strange re. N360 v3

Hello!

 

A client of ours who uses Norton 360 v3.8 has noticed that his Microsoft documents have been marked like this (shown in the picture)

 

 

Is t2010-02-20_184304.pnghis caused by Norton scan ? I use Norton Antivirus and Norton Internet Security , have also installed N360 numerous times on different computers but I have never seen this ? 

 

Thanks!