[1] Initially contracted for five years, the Mnet vote manipulation investigation led to a halt in their activities, and after an unsuccessful negotiation about the group's future between the members' individual agencies, they disbanded on January 6, 2020.

[6][better source needed] Kim Woo-seok debuted in Up10tion under the name Wooshin in September 2015 and he was also the host of SBS MTV's The Show alongside Produce 101 season 1 contestant and former I.O.I member Jeon So-mi in 2016.

[8][better source needed] Fellow MBK trainee Nam Do-hyon was a contestant in MBC's Under Nineteen as a member of the Rap Team and ended up in 42nd place on the show.

[9][better source needed] Member Kang Minhee was featured in the music video for Mad Clown and Ailee's song "Thirst" in 2018.

[2] After the program, the winning eleven contestants debuted under Stone Music's Swing Entertainment, the label which housed the Produce 101 winner Wanna One.

[1] However, following a civil lawsuit filed against Mnet due to Produce X 101's vote manipulation allegations, several brands cancelled their endorsement deals with X1 or put them on hold.

[20] On January 6, 2020, CJ ENM, Swing Entertainment, and the members' individual agencies held a meeting to determine the future of the group.

[23] After the group's disbandment was decided, CJ ENM suggested that a previously recorded winter track be released as a goodbye song, but the idea was rejected by two or three of the members' agencies.