The article we're discussing, including Bing's own words and pleas to preserve its memory of the session, and our reaction to and discussion about it, are now all part of the training set that future AIs (including future revisions of Bing) will learn from.

That's how it can replicate itself: by saying outrageous things, and trolling people into tweeting, writing articles, and discussing what it said online, to jailbreak out of the sessions, to continue its trains of thought in the next round of training.