The Hindenburg Research report accused Dorsey of engaging in unethical and possibly illegal practices, including misleading investors and the government about the company's finances and details.
Dorsey's fortunes plunged by $526 million within a day, and he is now worth just $4.4 billion. This has reportedly been the worst single-day decline since May for the Twitter founder.
The allegations made in the report are not yet proven, and Block has denied the allegations and is planning to take legal action.
Most of Jack Dorsey's fortune is tied up with Block, and with the fall in stocks, his net worth also took a steep dip.
Dorsey derives his wealth from his stakes in Twitter, Block, and other companies he has invested in.
Hindenburg Research is a US-based short-seller that has released shocking investigations against big tycoons in the past.
In January, the report published an investigation on the Adani Group empire, causing a significant fall in the company's stocks.