Britney Spears -- Chewing Gum During 'X Factor' Interview

Britney Spears spoke to FOX cameras before she took the stage at yesterday's Upfronts ... and she did so while chewing a piece of gum. Ding dang, y'all!!!

Britney ditched the gum by the time she went in front of the advertisers ... so clearly someone caught a glimpse of Brit's red carpet faux pas and corrected it.

For what it's worth ... Simon Cowell was chewing away too!

The gum wasn't the only thing Britney was chompin' on during yesterday's festivities -- Brit took a few bites out of her fingernails, too.