He should ask Carissa about her own reasoning, before asking project management about the safety of what Carissa did, he thinks; it is not clear that everyone's incentives are perfectly aligned. But he should ask Carissa about it, soon.
...actually, wouldn't another obvious reason to take a few weeks to carefully manufacture headbands, be if they wanted to modify his headband. Or everyone's, for that matter. Hm. Also a thing to subtly inquire about.
"Maybe it's the wrong use of your time to ask, but if it can be said briefly, what are the consequences if an adversary manages to infiltrate one headband?"