The two pop divas have a history of shade.
The pair teamed up to sing Timberlake’s hit, ‘What Goes Around… Comes Around.’
The pop star also praised Jennifer Lopez as she slid into the singer’s DMs.
The singer and 'American Idol' judge also dished to ET about his friendship with Underwood's husband, Mike Fisher.
ET caught up with the Foster sisters at day 1 of the 2018 iHeartRadio Music Festival in Las Vegas.
The 'Heartbeat Song' artist opened up about her friend's brave and candid revelations.
ET caught up with Bryan at day 2 of the 2018 iHeartRadio Music Festival in Las Vegas.
ET caught up with the 22-year-old model at day 1 of the 2018 iHeartRadio Music Festival in Las Vegas.
ET spoke with Clarkson at day 2 of the 2018 iHeartRadio Music Festival in Las Vegas.
The 26-year-old singer pulled out of the iHeartRadio Music Festival on Friday night due to 'unforeseen circumstances.'
The iconic rock guitarist was in critical condition on Wednesday.
The singer and fashion designer gets brutally honest about 'pregnancy life.'
The 'Mad At You' singer releases her EP, 'Good Cry,' on Friday, Sept. 21.
ET breaks down the beef between these two rappers, which dates back to 2012.