Perhaps related, I also see this in gCal, usually for invites I haven't accepted yet. See image. Those are rectangular (so maybe it isn't just circular images).
Bug 1634171 Comment 20 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Perhaps related, I also see this in gCal, usually for invites I haven't accepted yet. See image. Those are rectangular (so maybe it isn't just circular images). What makes it perhaps NOT related, though, is that the pattern is always the same, a black square in the corner. The image shows the bottom right corner, but I've seen it in other corners, too.