In Star Trek Into Darkness, the Enterprise journeys to Qo'noS, and a large moon fragment strongly resembling the remains of Praxis, as depicted in Star Trek VI, can be seen. Co-writer Alex Kurtzman stated, "It certainly was inspired by Praxis, however, it's not specified, so we're leaving it open as to exactly what that moon was."  Roberto Orci agreed in a comment on Twitter, stating that the moon was "not specified as Paraxis [sic]. But could be."  This destroyed sole moon of Qo'noS is, however, identified as Praxis on screen, in a table of information. 
The novelization of Star Trek Into Darkness, confirms that the broken moon orbiting Qo'noS was Praxis.
The comic book prequel Star Trek: Khan revealed that the moon was destroyed as the result of a mission undertaken by John Harrison for Section 31 (who learns his true identity as Khan while on said mission).