Mysterious postgres process pegging CPU at 100%; no running queries

I have a recurring issue where a postgres process is pegging my cpu at > 100%. It's a strange one, you can see below the command is ./Ac2p20853 (surrounded by asterisks, added by me).

Running SELECT pid, datname, usename, query FROM pg_stat_activity shows nothing too interesting (to me at least). Simply a few inserts into pg_proc.

How would you go about debugging what is the issue here?

See below for output from ps, grepping postgres.

Thank you.

deploy@localhost:~$ ps auxww | grep ^postgrespostgres   590  0.0  0.3 309312 13768 ?        Ss   20:29   0:00 postgres: deploy template1 5.5.5.5(53394) idlepostgres  2264  0.0  0.3 309312 13748 ?        Ss   20:20   0:00 postgres: deploy template1 5.5.5.5(37818) idlepostgres  3079  0.0  0.3 309312 13776 ?        Ss   20:12   0:00 postgres: deploy template1 5.5.5.5(60006) idlepostgres  3809  0.8  0.0   4504  1656 ?        S    18:11   1:19 /bin/sh ./systemd**postgres  3862  167  0.1 252512  5464 ?        Ssl  18:11 265:06 ./Ac2p20853**postgres  5287  0.0  0.6 308388 24560 ?        S    Aug09   1:22 /usr/lib/postgresql/9.6/bin/postgres -D /var/lib/postgresql/9.6/main -c config_file=/etc/postgresql/9.6/main/postgresql.confpostgres  5289  0.0  2.1 308516 87096 ?        Ss   Aug09   0:01 postgres: checkpointer processpostgres  5290  0.0  0.5 308388 22832 ?        Ss   Aug09   0:04 postgres: writer processpostgres  5291  0.0  0.2 308388  8676 ?        Ss   Aug09   0:03 postgres: wal writer processpostgres  5292  0.0  0.2 309196 11972 ?        Ss   Aug09   1:03 postgres: autovacuum launcher processpostgres  5293  0.0  0.1 163724  5004 ?        Ss   Aug09   2:34 postgres: stats collector processpostgres  6065  0.0  0.3 309312 13824 ?        Ss   20:04   0:00 postgres: deploy template1 5.5.5.5(51616) idlepostgres  7384  0.0  0.3 309312 13832 ?        Ss   20:40   0:00 postgres: deploy template1 5.5.5.5(55916) idlepostgres 11467  0.1  4.0 328788 161612 ?       Ss   Aug09  10:50 postgres: deploy db_production [local] idlepostgres 11638  0.0  4.3 339336 174368 ?       Ss   Aug09   4:52 postgres: deploy db_production [local] idlepostgres 11812  0.0  0.5 316092 21496 ?        Ss   Aug09   0:00 postgres: deploy postgres [local] idlepostgres 12707  0.0  0.4 315660 16820 ?        Ss   Aug09   0:00 postgres: deploy db_production [local] idlepostgres 17511  0.0  0.3 309312 13716 ?        Ss   20:33   0:00 postgres: deploy template1 5.5.5.5(33460) idlepostgres 17968  0.0  0.3 309312 13804 ?        Ss   20:44   0:00 postgres: deploy template1 5.5.5.5(34548) idlepostgres 18974  0.0  0.3 309312 13768 ?        Ss   20:16   0:00 postgres: deploy template1 5.5.5.5(52290) idlepostgres 19017  0.0  0.3 309312 13752 ?        Ss   20:24   0:00 postgres: deploy template1 5.5.5.5(37348) idlepostgres 21120  0.0  0.3 309312 13788 ?        Ss   20:08   0:00 postgres: deploy template1 5.5.5.5(33084) idlepostgres 24189  0.0  0.3 309312 13744 ?        Ss   20:36   0:00 postgres: deploy template1 5.5.5.5(35660) idlepostgres 31498  0.0  0.3 309312 13804 ?        Ss   20:48   0:00 postgres: deploy template1 5.5.5.5(39618) idle