That's almost a 10% drop in the share price. Based on a Market Cap of $20B, that's a $2 Billion dollar move, all based on security vulnerabilities. But I'll bet that there wasn't enough money at St. Jude for a proper security design.
The story so fartl;dr: hackers drop 0day on medical device company hoping to profit by shorting their stock
I expect to see more of this.