







Apparently, somebody didn't get the memo. On the afternoon of July 3, the Nasdaq stock exchange closed three hours early in advance of the Independence Day holiday. At that time, Nasdaq—in a test that had been announced to its data partners a week before—pushed out some manufactured stock quote data as part of a test of its systems. However, some of that data was apparently published inadvertently by multiple financial websites, including Google and Bloomberg.

The data errantly published was sent as part of a test of Nasdaq's UTP ("unlisted trading privileges") Quotation Data Feed, which serves up quotation data to a collection of market data vendors. "As part of its normal process, Nasdaq distributed test data and certain third parties improperly propagated the data," a Nasdaq spokesperson told Ars via e-mail. "Nasdaq is working with these third party vendors to resolve the matter."

As a result, people monitoring stocks such as Apple and Amazon got a bit of a late-day shock—wild fluctuations in price quotes. At 7:30pm Eastern time, a quote for Amazon showed the company's stock price at $123.45, which would have been an 87.25 percent drop from its actual value. Apple's stock followed suit, to the same $123.45 value, at 7:56pm Eastern Time. (A few minutes later, Apple stock surged back to $645.713, what would have been a 348 percent apparent gain.) Microsoft also saw wild price quote fluctuations—at one point, the company would have been valued at $1 trillion based on the Nasdaq data published.

Third parties that published test data included Bloomberg and ICE Data Services (formerly Interactive Data Corporation. ICE is now a unit of Intercontinental Exchange—the company that now owns the New York Stock Exchange). Ars reached out to both of these companies for comment but did not get a response.

Since the markets were closed, luckily no trades could be executed based on the data. The only real-world impact may have been some panic attacks and heart palpitations. Still, the episode shows how much of an impact the corruption of market quote data could potentially have. Even back in 2013, an interruption in Nasdaq data forced the exchange to pause trading. (That problem, caused by a network issue between Nasdaq and one exchange participant, has long since been resolved.) And potential problems like that are exactly why Nasdaq frequently tests its systems after hours to verify network throughput.

Listing image by Getty Images | Gary Waters