Short sellers betting against online food delivery service GrubHub Inc.'s (GRUB) shares can feast and pop champagne after the company's stock cratered over 40% on Tuesday, its worst daily performance ever. Crushed by competition from rivals like Uber Technologies Inc. (UBER), Doordash and Postmates, the firm missed third quarter earnings estimates and announced fourth quarter guidance below analyst expectations. The stock fell to $33.11 and is down 57% year-to-date.

GrubHub shorts saw their net-of-financing mark-to-market profits climb by $504.4 million on the price plunge, according to S3 Partners, bringing their total mark-to-market profits for the year to $874 million.

As of Wednesday, total short interest in the company was $1.20 billion with almost 21 million shares shorted, making it the fourth largest short in the Internet & Direct Marketing sector following Inc. (AMZN), Booking Holdings Inc. (BKNG) and Wayfair Inc. (W). It is also the most profitable short in the sector for investors this year.

Those who predicted GRUB shares dropping increased their short exposure by 1.02 million shares over the last two months. Last week alone accounted for short selling increasing by 193,000 shares even though the stock was on an uptrend, noted the financial technology and analytics firm in a note published yesterday. Below is a chart comparing stock price and shares shorted over time.

S3 Partners

GRUB shares shorted hit a year-to-date high of 22.86 million shares in mid-August, but Ihor Dusaniwsky, managing director of predictive analytics at S3, says the stage is set for shares shorted to hit a new high by the end of the year.

"Increased competition from the likes of Uber and DoorDash will continue to put pressure on GrubHub’s bottom line and increase the cost of customer acquisition and retention," he said. "Short sellers have been re-building their exposure over the last month and a half and with today’s windfall of mark-to-market profits we expect more short sellers to belly up to the table and order up more GRUB short sales."