It turns out that Justin Bieber has reportedly been carrying on a secret relationship with Kendall Jenner ever since he reunited with on-and-off-again girlfriend Selena Gomez in June.

Bieber recently sparked cheating rumors when he was spotted on an intimate dinner date with Jenner at Ferdi, a restaurant in Paris, France -- he apparently told Gomez that he was "grabbing dinner with his security team."

What was the "Come & Get It" singer's immediate reaction when she learned the truth? "She went crazy," an insider told InTouch Weekly. "Selena was absolutely livid when she found out Justin had dinner with Kendall. He lied to her about it."

"She was so angry that she changed her flight to come back to L.A. two days early and told him their relationship was over -- again," the insider continued. "She told Justin she wanted to have nothing to do with them. That meant he had to cut them off, too."

Following her trip to the Coachella Valley Music & Arts Festival with Kendall and Kylie Jenner back in April, Gomez cut all ties with the reality stars after she saw flirty texts from them on Bieber's phone.

Knowing how the "Spring Breakers" actress feels about the Jenner sisters, the Canadian pop star reportedly continued to text and hang out with the model. "It turns out Justin has been texting Kendall the whole time and Paris wasn't the first time they secretly had dinner together," the insider said. "Justin admitted it and insists they're just friends, but Selena doesn't believe him, and they had a screaming match over it. She feels completely humiliated."

"Kendall just loves that she got something over on Selena," the insider added. "It's ugly behavior."

Although Justin Bieber insists that he is just friends with Kendall Jenner, Us Weekly also reported that he and Selena Gomez "fought and split," since the latter simply "doesn't trust Kendall's motives."