Adding fireballs or creepers to a team with friendly fire disabled still deal damage to its teammates.

Adding fireballs to team A
Adding creepers to team A

>>

Fireball and creeper does damage to team A

The creeper will not target the player itself but the explosion still harms its teammate. The fireball simply ignores it, deals damage regardless.

Steps to reproduce:
1.) Create a team and add yourself and the fireball to team.
2.) Disable friendly fire via team options.
3.) Hit fireball.