Krispy Kreme, Opendoor, Rocket and Kohl’s are merely the public face of a summer boom in bets by private traders.

If you thought meme stocks had ridden off into the sunset, think again. Shares of companies such as Krispy Kreme and Kohl’s saw unusual surges starting in mid-July. The frenzy earned the “DORK” label ...

The S&P 500 hit multiple record highs over the past month, rallying against US policy uncertainty, but experts warn that the ...