Slack has not had a good week. On the heels of a CNBC report that Microsoft Teams is maintaining its lead over the messaging service, The Wall Street Journal (WSJ) is reporting that the Securities and Exchange Commission (SEC) has opened an investigation into Slack, among others.

According to the WSJ, “the SEC is probing IPOs over the past several years of other so-called unicorns, companies known for achieving high valuations while private.”

The SEC’s staff evidently sent letters to Citadel Securities LLC to inquire about “how it opened Slack’s stock for trading on June 20 in the workplace-messaging app’s so-called direct listing.”

As the WSJ points out, there is no indication what type of wrongdoing the SEC is looking for, or who may be the specific target of the investigation. Nonetheless, an SEC investigation is the last thing any company wants.