Josh also touched on his negative experience while filming the Teenage Dream video back in 2009.
"When other people were around she was cold as ice even called the act of kissing me “gross” to the entire set while filming," he said.
WATCH: Katy Perry takes off Josh Kloss' pants in 'Teenage Dream' music video
He also claims Katy invited him to a strip club (an invite he declined) and that he only made $650 for the job, despite it appearing on her video and tour.
The now 38-year-old explains that reps urged him to keep quiet, but he had decided to use the anniversary to to break his silence.
"I was lorded over by her reps, about not discussing a single thing about anything regarding Katy publicly. And a couple interviews they edited and answered for me," he said.
He finished with "So, happy anniversary to one of the most confusing, assaulting, and belittling jobs I’ve ever done. Yay #teenagedream"
Josh's post highlights the double standard that can exist around sexual assault.
It's important to note that the allegations are currently just that — allegations — as Katy hasn't addressed the claims yet. But sexual assault is always something that should be taken seriously — whether the victims are male or female.
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If you or someone you know is affected by sexual assault or family violence, call the 1800RESPECT hotline or visit www.1800respect.org.au/. You can also call the Domestic Violence Hotline on 1800 656 463.