Consider the attached sample document created in Microsoft Office, finally saved in Office 365. When viewed in Office 365 there is a green blurry border around each of the images on the slide. In LibreOffice 6.2.5.2 as well as 6.4.0.0.alpha0+ those borders are simply missing (though retained, i.e., when editing the document in LibreOffice and then viewing in Office again, nothing seems lost).
Created attachment 152790 [details] Sample slide (PPTX)
Created attachment 152791 [details] How it should look (e.g., Office 365)
Created attachment 152792 [details] How it actually looks (LibreOffice)
That is the "Glow" effect. It is a missing feature, same as other effects. We should consider to make such reports duplicate to bug 101181.
*** This bug has been marked as a duplicate of bug 101181 ***