Skeptics have not missed the opportunity to jump on the tech sector sell-off. Apple shares have lost a combined 6.2 percent over the last two trading sessions, and short sellers have increased their positions to $9.1 billion, up 54 percent year-to-date and nearing the 2017 high of $9.7 billion, according to data from financial analytics firm S3 Partners. 

Apple Inc. (AAPL) shareholders were dealt a blow Monday when Mizuho Securities became the second firm to downgrade the Silicon Valley giant to neutral from buy. Mizuho Securities noted that enthusiasm among investors and year-to-date performance is priced in, meaning they see limited upside for the iPhone maker. (See also: Apple Receives Second Downgrade in a Week

News of the downgrades is welcome news for the bears who have had a rough 2017. Monday's sell-off netted $335 million in mark to market gains for short sellers, taking losses for the year back towards $1 billion. Apple is part of a small group of tech giants that have significantly outperformed the Nasdaq in 2017, dragging the index to all-time highs. However, the famed FAANG stocks came back to earth Monday when in the space of two trading days they lost a combined $126 billion. "AAPL’s increase in short interest is not a case of the tech tide lifting all boats," Ihor Dusaniwsky of S3 Partners said in a note. 

"While short interest in both AAPL and the Powershares QQQ Nasdaq 100 ETF (QQQ US) traded in tandem for most of the year, we can see an obvious divergence in mid-May. While QQQ short interest fell by $316 million, or 4%, since May 15th, AAPL short interest increased by $1.3 billion, or 17%, since May 15th."

Source: S3 Partners

According to S3 Partners, Apple is now the third-biggest short in the market behind Alibaba Group (BABA) with $16.7 billion in short interest, and electric car maker Tesla Inc (TSLA), which saw short interest in its company top $10 billion last week. (See also: Elon Musk To Doubters: "These Guys Want Us To Die")