Does Fox-Fire target, and what happens if the targets' Might is increased above 4 in response?

Ruling: Fox-Fire targets. If the total Might of the targets becomes illegal (over 4) upon resolution, you choose a subgroup from among the initial targets that is still legal (4 Might or less).

Sequence:

• Fox-Fire is cast and targets are chosen
• If a reaction spell increases the targets' Might above 4
• Upon resolution, choose a subgroup of the initial targets with total Might of 4 or less