After U.S. markets closed Monday and were opening in the Far East, test data inadvertently went live causing some Nasdaq stock quotes to be reported incorrectly. No actual trades were affected, however, and the glitch did not affect quotes on any New York Stock Exchange stock.

The faulty data reset the per share price for several stocks at exactly $123.47. That caused Apple Inc. (NASDAQ: AAPL) to drop 14%, Amazon.com Inc. (NASDAQ: AMZN) to plunge 87% and Microsoft Corp. (NASDAQ: MSFT) to soar 79%. Had the changes actually happened, Apple would have lost $104 billion in market cap, Amazon would have lost $396 billion and Microsoft would have added $415 billion.

A report in The Wall Street Journal offered two possible causes for the mishap. A Nasdaq spokesman attributed the error to faulty test data that had been improperly disseminated by vendors like Bloomberg. At least one person laid the blame at Nasdaq’s feet, saying that the exchange had changed its testing protocols without informing vendors in advance.

A Nasdaq spokesperson said there was no evidence that the glitch was due to a hacking attack. One possible explanation for the glitch is that Monday’s shortened trading schedule played a part in the spread of the test data.

According to the Financial Times, a total of 13 companies, including Zynga Inc. (NASDAQ: ZNGA) and Sears Holdings Corp. (NASDAQ: SHLD) saw shares rise to $123. For Zynga, that represented a 3,000% boost, and for Sears, a 1,000% surge. Four companies, including Amazon and Alphabet Inc. (NASDAQ: GOOGL) fell more than 85% as a result of the glitch.

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