Shares of the payments company Block were in free fall Thursday, after a short seller accused the Jack Dorsey-run business of fraud.

Hindenburg Research, a respected short seller, said Block (formerly known as Square) allowed criminal activity to operate and flourish by taking a “Wild West” approach to compliance, which “made it easy for bad actors to mass-create accounts for identity fraud and other scams, then extract stolen funds quickly.”

The accusations came after what the firm said was a two-year investigation. The main focus of criticism was Block’s Cash App, a peer-to-peer payment platform that lets users send money to friends and family.

“CEO Jack Dorsey tweeted that users could get government payments through Cash App ‘immediately’ with ‘no bank account needed’ due to its frictionless technology,” the report reads. “Within weeks of Cash App accounts receiving their first government payments, states were seeking to claw back suspected fraudulent payments—Washington State wanted more than $200 million back from payment processors while Arizona sought to recover $500 million, former employees told us.”

It’s Cash App’s alleged criminal ties that are among the most riveting accusations. The report says the platform was quickly embraced by bad actors since it was easy to remain anonymous (using false identities) and, should their accounts be closed, they could quickly get back on the platform.

Block did not respond to a Fast Company request for comment about the report. In a statement to CNBC, however, the company said, “We intend to work with the SEC and explore legal action against Hindenburg Research for the factually inaccurate and misleading report they shared about our Cash App business today. . . . Hindenburg is known for these types of attacks, which are designed solely to allow short sellers to profit from a declined stock price. We have reviewed the full report in the context of our own data and believe it’s designed to deceive and confuse investors. We are a highly regulated public company with regular disclosures, and are confident in our products, reporting, compliance programs, and controls. We will not be distracted by typical short seller tactics.”

Cash App is mentioned in hundreds of hip-hop songs, with artists claiming to use it for everything from drug trafficking and prostitution to paying hit men. (Dorsey, the report notes, bragged about the app’s popularity with music artists at a JPMorgan investor conference in May 2020 and again in 2021.)

Block seemed to embrace the controversy, promoting a video for a song called “Cash App,” which described paying contract killers through the app.

“The song’s artist was later arrested for attempted murder,” the report reads. “There is even a gang named after Cash App: In 2021, Baltimore authorities charged members of the ‘Cash App’ gang with distribution of fentanyl in a West Baltimore neighborhood, according to news reports and criminal records.”

The Hindenburg report further alleges that Cash App ignored concerns from both employees and users even as alleged “criminal activity and fraud ran rampant on its platform.”

“This appeared to be an effort to grow Cash App’s user base by strategically disregarding Anti Money Laundering (AML) rules,” it reads.

Hindenburg also alleges former employees told it that Block had disregarded “Know Your Customer” laws, which require financial institutions and financial services companies to establish a customer’s identity.

In an attempt to confirm this, the firm says it opened accounts under the names of Donald Trump and Elon Musk, quickly acquiring a Cash App debit card bearing Trump’s name.

“Former employees estimated that 40% to 75% of accounts they reviewed were fake, involved in fraud, or were additional accounts tied to a single individual,” the report said.

Hindenburg Research is an activist short seller, but the company’s track record is admired among investors. Two months ago, it issued an explosive report focused on Adani Group that erased $100 billion off the Indian conglomerate’s market cap. Other affected companies include Clover Health and Nikola. Since 2020, Bloomberg reports, the company has targeted roughly 30 businesses, which saw their shares drop 15% on average the next day.

“We think Block has misled investors on key metrics, and embraced predatory offerings and compliance worst-practices in order to fuel growth and profit from facilitation of fraud against consumers and the government,” Hindenburg wrote. “We also believe Jack Dorsey has built an empire—and amassed a $5 billion personal fortune—professing to care deeply about the demographics he is taking advantage of. With Dorsey and top executives already having sold over $1 billion in equity on Block’s meteoric pandemic run higher, they have ensured they will be fine, regardless of the outcome for everyone else.”