The NASA news item From Pedicures to the Peregrine Rocket, Paraffin Wax Proves Its Worth says:
The paraffin-based fuel also works under challenging environmental conditions, like the very low temperatures found on the surface of Mars. The Mars Ascent Vehicle, currently under development by NASA’s Jet Propulsion Laboratory, aims to use the paraffin technology to return a sample from the surface of the planet to an orbiting spacecraft.
Two years on, have the tests gone well? Is paraffin still the plan?
For more, see the (currently unanswered) question Why NASA's sudden (apparently) interest in Wax hybrid engines? Which property is so attractive now?