KEY POINTS
  • Slack shares plunged 20% on a disappointing forecast for the fiscal first quarter. The company cited coronavirus concerns in its guidance.
  • The stock sank along with the broader market during regular trading on Thursday.
  • Revenue for the fourth quarter topped estimates.

Slack shares plunged in extended trading on Thursday after the maker of messaging software provided a disappointing forecast for the fiscal first quarter, citing uncertainty surrounding the coronavirus.

The stock sank more than 20% to $17.03. That adds to an almost 10% drop during regular trading, as the shares fell alongside the broader market, which had its worst day since 1987.