About exploits on lootboxes in overwatch

There was a trick if you gather loot boxes and wait until some friend get a legendary you should instantly open 2 or 3 so you can easily get a legendary on each loot box.

That trick was patched after halloween event.

There are any other tricks for loot boxes?

Dont know about such exploid. afaik the lootboxes are determined as soon as you receive them since always.