The online war of words appears to have started with would-be subs Cuban threw Cardi's way -- at least that's how CB took it, because she immediately responded with extra firepower. A lot of Cuban's tweets have since been deleted, but Cardi's got the receipts.

According to Cardi, this all began when Cuban tweeted Saturday ... "I pray a man don't marry me just to cheat on me ... that's next level OD DISRESPECT." Cardi apparently responded to that, which set Cuban off ... and Cardi replied again in kind.

That's where things get interesting on Cuban's part ... because she appears to switch up her story here about what exactly went down back in 2018, when Offset was allegedly texting Cuban's friend to solicit a 3-way with all of them (sans a then-preggo Cardi).

Here, Cuban says Offset was, in fact, trying to "f*** me" ... different from what she told us at the time, when she denied ever meeting him or knowing anything about the drama at all. When Cardi hit her with DMs they exchanged at the time -- in which Cuban also denied any knowledge about the sitch -- Cuban asserted she'd been paid off to cover Offset's mess.

Cardi fired back, writing ... "First you said the girl was no longer ya friend, then it turned to he was fuckin her, now it’s he was trying to fuck with you? You can’t even keep up with ya own lies. Show me the receipts. You started this yet asking me what does it prove? Honey you need this moment not me."

In the end, this may well be a mistaken interpretation on Cardi's part. Cuban ended the back and forth with ... "You can't get mad I said I don't listen to your music !? Bitch it's been years the husband tweet was not bout u! It's just got that's made u mad girl bye your weird."

You might recall ... Cardi and Offset briefly split up because of this alleged philandering, but ended up getting back together, getting hitched and having more kids.