opportunistic

adj

1. Taking advantage of situations that arise.

   “The danger now isn't so much from the AIDS virus itself as from opportunistic infections.”

2. Taking advantage of situations to advance one's own interests without regard for moral principles.

   “You can't trust somebody that opportunistic: he'll stab you in the back the first chance he gets.”

   “[…] an opportunistic relative masquerading as his rescuer, […]”

   “Now, maybe you see this as sort of an obvious and opportunistic publicity play by a competing social-media service. Maybe it even seems crass to you—a little grave-dancy.”