https://metaculus.com/questions/17176/ai-takes-down-stock-exchange-before-2025/

Erratic trading in stock markets like the NYSE, NASDAQ, and LSE is an increasing problem, though as of May 2023, not directly due to AI, though perhaps due to high-frequency trading (HFT).

2010 drop of 1,000 points in the DOW for disputed reasons

2022 European stock flash crash due to human error

In May 2023, a deepfake image showed an explosion at the US Pentagon, which was picked up by media and caused a 

In all of these cases, prices recovered quickly and no exchanges were halted.