  The paradigm of second-order phase transitions (PTs) induced by spontaneous
symmetry breaking (SSB) in thermal and quantum systems is a pillar of modern
physics that has been fruitfully applied to out-of-equilibrium open quantum
systems. Dissipative phase transitions (DPTs) of second order are often
connected with SSB, in close analogy with well-known thermal second-order PTs
in closed quantum and classical systems. That is, a second-order DPT should
disappear by preventing the occurrence of SSB. Here, we prove this statement to
be wrong, showing that, surprisingly, SSB is not a necessary condition for the
occurrence of second-order DPTs in out-of-equilibrium open quantum systems. We
analytically prove this result using the Liouvillian theory of dissipative
phase transitions, and demonstrate this anomalous transition in a paradigmatic
laser model, where we can arbitrarily remove SSB while retaining criticality,
and on a $Z_2$-symmetric model of a two-photon Kerr resonator. This new type of
phase transition cannot be interpreted as a "semiclassical" bifurcation,
because, after the DPT, the system steady state remains unique.
