A new Twitter battle seems to be brewing, and no, it doesn't involve President Trump.

CNN anchor Jake Tapper took exception to former Fox News host Bill O'Reilly's Twitter comment on his "low" viewership ratings, by unleashing a withering response on the social media platform Wednesday.

O'Reilly congratulated Fox News network host Sean Hannity for "kicking serious butt in the ratings" but not before mocking Tapper's ratings for being "low as you can go."

Minutes later, Tapper slammed O'Reilly.

"'Low' would be sexually harassing staffers and then getting fired for it — humiliated in front of the world," Tapper said on Twitter. "Now THAT would be low."

Back in April, O'Reilly was ousted from Fox News following a scathing article in The New York Times that reported he or the company made payouts totaling about $13 million to five woman involving allegations of inappropriate behavior by him over several years.

Last month, Hannity moved his cable news show to the 9 p.m. ET as part of the network's ongoing reshuffle caused by O'Reilly exit, and even hosted his former colleague on his program.

Contributing: Doug Stanglin