If you put a horse on a lead then push them through a nether portal, the lead drops on the ground but it is still in your hand and it dupes the lead.
Linked issues
Comments 2
Dupe of MC-15270
MC-66530
Dupe Bug
Resolved
Duplicate
0
Adam Duke
(Unassigned)
Unconfirmed
Minecraft 14w32d
Retrieved
This may affect 1.7.10 and other snapshots. I have not tried it so I can't tell you if it does or not.