Ligat Ha'Al champions Hapoel were edged out 2-1 at home by Romanian side FCSB in a game where all the goals came in the final 15 minutes.
Hapoel were denied by the reflexes of FCSB goalkeeper Florin Niță, who made smart stops either side of half-time.
Two sharp finishes from super-sub Harlem Gnohéré in the space of five second-half minutes put the visitors in charge.
Isaac Cuenta, another substitute, gave Hapoel a late lifeline with a close-range finish but FCSB held on.