If it's not coming out the threads between either the nozzle and the block at the bottom or the heatbreak and the block at the top (which would indicate a wrong assembly), then it's most likely filament that's being caught and crawled up between the silicone sock and the block.
Heat up the hotend to ~120°C, then *turn off the machine*.
Then carefully take off the silicone sock and clean the parts by removing all that squished filament.
Reapply the sock and print sth. Once done, take off the sock again and inspect the top and the bottom to see if filament squishes out at the abovementioned threads. If that's *not* the case, everything is fine and you just need to clean your hotend more often.