YouTube stars Trevor “TmarTn” Martin and Tom “ProSyndicate” Cassell have been embroiled in a controversy involving the promotion of CSGOLotto.com, a Counter-Strike: Global Offensive weapon skin gambling website they own but did not disclosed a connection to.

Both Martin and Cassell have posted numerous videos in which they gamble weapon skins using CSGOLotto and are shown winning large sums of money, reacting with surprise and elation when they do.

YouTube user HonorTheCall investigated CSGOLotto and found that Martin is the director of the website, while Cassell is the vice president. During many of their skin gambling videos, CSGOLotto is promoted as a service, but their stake in the website is never clearly stated.

CSGOLotto allows players to add weapon skins to a pot and then, using a random number generator that functions similar to a slot machine, one of them is awarded the entire pot.

These skins are unlocked by playing Counter-Strike: Global Offensive on Valve’s digital games platform, Steam. Since they are designed to be bought, sold, and traded within the Steam ecosystem, they are assigned a real money value based on rarity.

Thanks to third-party services outside of Steam, it has become possible to cash weapon skins out and earn real money. In recent years, gambling these skins has also become very popular and, according to a Bloomberg report, as much as $2.3 billion worth of skins were bet in 2015.

As highlighted in a YouTube video by h3h3Productions, skin gambling isn’t regulated in the same way that the traditional gambling industry is. Since CS:GO is often played by a younger audience, the marketing of a gambling site is potentially being aimed at the underage, which places it in murky legal territory.

Martin and Cassell’s failure to disclose their interests in CSGOLotto violates YouTube guidelines and has also called into question the authenticity of the videos. It has been suggested that they may have been able to fix the outcome of bets in order to stage videos.

Martin has since posted a video downplaying his involvement with CSGOLotto. It was later deleted but has been archived.

“What’s breaking news now is that myself and a few other people including [ProSyndicate] own CSGOLotto. This is something that has never been a secret. I don’t understand why it’s breaking new now,” he said.

“It’s never been under wraps. It’s never been secret. We’ve never gone around bragging about it saying, ‘Oh yeah we own the site’ all over social media. But it’s also never been a secret, it’s been mentioned in videos before, on livestreams before … it’s never been this big scary, hidden thing that people are making it out to be.”

The h3h3 video alleges that a team of researchers was not able to find any examples Martin or Cassell disclosing their ownership of CSGOLotto. Instead, there are videos where the two promote the website as users.

“We found this new site called CSGOLotto,” Martin said in one video. “We were betting on it today and I won a pot … it was the coolest feeling ever.”

Since then, the YouTube descriptions for Martin’s skin betting videos have been updated to highlight a collaboration with CSGOLotto. Originally, they simply linked to the website. Additionally they also now advise the underage not to play as it is illegal in some jurisdictions.

Cassell, meanwhile, has Tweeted an apology, but also stated he feels his disclosure was sufficient.

Counter-Strike: Global Offensive developer and publisher Valve has also recently come under fire for the gambling element of its CS:GO skin economy.

On June 23, Counter-Strike: Global Offensive player Michael John McLoed filed a class action lawsuit alleging that Valve has allowed an illegal online gambling market to develop.

As reported by Polygon, the suit states Valve Corporation “knowingly allowed … and has been complicit in creating, sustaining, and facilitating a market” where skins can be gambled. This, it claims, is done by allowing Steam accounts to be linked to third-party websites.

“In the eSports gambling economy, skins are like casino chips that have monetary value outside the game itself because of the ability to convert them directly into cash,” the suit reads.

“In sum, Valve owns the league, sells the casino chips, and receives a piece of the casino’s income stream through foreign websites in order to maintain the charade that Valve is not promoting and profiting from online gambling, like a modern-day Captain Renault from Casablanca,” the suit continues.

“That most of the people in the CS:GO gambling economy are teenagers and under 21 makes Valve’s and the other Defendants’ actions even more unconscionable.”