Da Internz - who worked with Rihanna on the track - claim that the newly added cameo in the song will leave fans stunned.
"We got the Rihanna [track] 'Birthday Cake' coming out in a week. And the feature on there is gonna shock the world." Kosine told MTV News on the red carpet at the ASCAP Rhythm and Soul Brunch.
"It's gonna be crazy," his production partner Tuo added.
The track includes the lyrics: "I know you wanna bite this/ It's so enticing... Nothing else like this, I'm a make you my bitch/ And it's not even my birthday / But you wanna put your name on it."
Reports have claimed that Rihanna was recently spotted leaving the same West Hollywood recording studio as ex-boyfriend Chris Brown, who she split up with after he assaulted her.
Brown pleaded guilty to the charges in June 2009 and was sentenced to five years' probation.
Kosine said: "All I'm gonna say is stay tuned - it's dropping [this] week."
Tuo also added that fans should also expect a video clip with the audio, explaining: "The visual has to go with it because everybody's going to be like, 'Oh my god!'
Watch Rihanna's video for 'S&M' below: