opportunistic

Taking immediate advantage, often unethically, of any circumstance of possible benefit.

taking immediate advantage, often unethically, of any circumstance of possible benefit; practising opportunism.

Causing disease only when the immune system of the host has been weakened, or other damage to the host provides special opportunity for invasion; — of microorganisms or infectious diseases.

taking advantage of situations that arise

said of people who will take advantage of situations to advance their own interests, without regard for principles

taking immediate advantage, often unethically, of any circumstance of possible benefit