  We conjecture and verify a set of universal relations between global
parameters of hot and fast-rotating compact stars, including a relation
connecting the masses of the mass-shedding (Kepler) and static configurations.
We apply these relations to the GW170817 event by adopting the scenario in
which a hypermassive compact star remnant formed in a merger evolves into a
supramassive compact star that collapses into a black hole once the stability
line for such stars is crossed. We deduce an upper limit on the maximum mass of
static, cold neutron stars $ 2.15^{+0.10}_{-0.07}\le M^\star_{\mathrm{TOV}} \le
2.24^{+0.12}_{-0.10} $ for the typical range of entropy per baryon $2 \le S/A
\le 3$ and electron fraction $Y_e = 0.1$ characterizing the hot hypermassive
star. Our result implies that accounting for the finite temperature of the
merger remnant relaxes previously derived constraints on the value of the
maximum mass of a cold, static compact star.
