No, not really. You need to risk a lot of capital to make any money at all.

For instance, to make even $10,000 on a 5% drop in Facebook stock, you would need to sell short $200,000 in Facebook stock and would need to have $100,000 in cash deposited with a broker (initial margin). If the stock goes up by even a penny, you would need additional margin to cover that. A young hacker with no money cannot make any by shorting stocks.

You could create a much more leveraged position with options. With a put option buy, your maximum loss is capped, so you wouldn't need any additional margin.

Uh, no. How many security exploits do you think would impact Facebook's stock? This one? Investors do not care about minor bugs that are fixed quickly.

Simultaneously use the exploit on many investors' FB pages, perhaps starting with their children and families. Nobody cares about an exploit used on Zuck's wall and fixed soon after, but the perception would change if it was more personal and widespread.

This bug is a spammers paradise though, free advertising by posting on other people walls about products. Gold

That would work great, in a James Bond movie.