If any site that takes KYC documents and sells the document to another party, then howcan to identify that if they do not disclose and/or if they do not mention about the data breach. As the data can be shared from various sites, we usually use various types of websites each day.
Many websites we visit and submit our personal information to are most times because we trust them, you can’t just give your personal details to a website you just come across without knowing of their virility with such informations. It may not be easy to know the site that may have sold your data out, but it is also much possible that it may be the most recent one you’ve uploaded your personal information to especially if you have some reservations about them at the time of even registering and providing this personal details. That is why you only give your personal info to where is trusted and have good reputation of trust from existing users.
Any site at all can sell out your information and the criteria for not doesn't depend on how new or old such a site has been operating or you the user just having to use it for the first time. Moreover, that you're using a site for the first doesn't make them liable of selling out your informations. We won't know even if the site we most trusted are the ones giving out our information until they are exposed. So no need trusting any centralized platforms be it old or new.
For sure there's some information would leak if it happens that the platform or casino sell out the personal data's of their costumer. But for sure it will not happen on reputable platform since they can earn more from engagement of their gamblers rather than doing that activities.
Mostly the one doing that are small platforms which didn't gather yet a good reputation.
Maybe if they failed on their operation there's instances that this situation will happen especially if the casino owners or those who handle those data's are desperate to gain money even if they do a illegal things like selling those private details of their costumers.