According to Barron's columnist Steven Sears, someone made a big bet against the financials ETF yesterday (ticker symbol XLF), and it has everybody buzzing.

The trader bought 100,000 put options on the ETF (a put option increases in value when the price of the underlying asset, in this case, the ETF, goes down).

To put that number in perspective, Sears writes, "Few investors ever trade more than 500 contracts, so a 100,000 order tends to stop traffic and prompt all sorts of speculation about what's motivating the trade." According to Sears, the trade "has sparked conversations across the market."