NEW YORK, NY - OCTOBER 23: Shawn Mendes (L) and Camila Cabello visit "The Elvis Duran Z100 Morning Show" at Z100 Studio on Oc
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Canadian singer-songwriter Shawn Mendes and Fifth Harmony standout Camila Cabello have delivered a good old-fashioned teen duet with "I Know What You Did Last Summer," which was teased for over a week and released late last night.

Set to appear on Mendes' Handwritten Revisited reissue, the song finds Mendes and Cabello trading verses about perceived infidelity as the intensity gradually increases. Cabello recently shared that the song was pieced together during a backstage meeting at Taylor Swift's 1989 world tour this summer.

Mendes and Fifth Harmony each enjoyed breakout years in 2015: the former scored a No. 1 album and toured with Swift, while 5H enjoyed a Top 20 mainstay with "Worth It." Both Mendes and the girl group have stated that they're already working on new music.

Click here to watch our new interview with Cabello's Fifth Harmony sister, Ally Brooke Hernandez, about her latest charity work.