Good question.
There are many places in Philippines that I had never been and it has nothing to do with safety. You are most likely to get robbed in Manila than anywhere else. A Korean man was robbed and shot(killed) in Malete in Manila in Mar this yr. Two Japanese were robbed at gun point in Makati couple of wks ago!!! Malete is the area where Si-Kat departs to PG everyday for umpteen yrs. Is Manila safe?
I assumed your question is on terrorism. There had been a few cases over last 25yrs when foreigners were target by terrorist group but it is extremely rare. The most famous incident happened in 2000 at Sipadan(Sabah in East Malaysia), hostages were taken and sent to Jolo in Philippines. The rest is history.
I have seen video on youtube by a foreign tourist about his trip to Basilan which is supposed to be the most dangerous place in the country!!
Marawi City in 2017 witnessed a five month battle between Gov forces and the militants. Two yrs ago a bomb killed four at a Catholic Mass there.
I need a good reason to travel to a strange place and scuba diving is the only reason that I visit Philippines. So you will not see me visiting Marawi and Basilan. There are many places where scuba diving is available in Philippines but lack of detail information and review has deterred me from visiting. I am NOT that adventurous after all.