The bug

You can use a flint and steel on a creeper when it is already ignited, causing the item to lose durability for no reason.

To reproduce

1. Summon an ignited creeper with a long fuse:

/summon minecraft:creeper ~ ~ ~ {ignited:1,Fuse:2000}

2. Use a flint and steel on it.
3. It will be successfully used everytime.