I also got one of these emails for one of my sites and looked at the “security researcher” that found the vulnarability: He has somehow found hundreds and hundreds of vulnarabilities in websites today. Wonder how he did that. Must have been lots and lots of work *sarcasm sign*. The sites also seem to be pretty much in alphabetical order.
And you are supposed to write the “researcher” so they can tell you what the problem is. It’s probably no coincidence that they also explain how to pay them via PayPal …
In other words: Even if the platform itself is legit (and I am not convinced it is), there are people who find a vulnarability in WordPress or a WordPress plugin and instead of disclosing this to WordPress or the author of the plugin, they use this platform to automatically send these emails to all sites they can find with the same setup. And then they hope people will give them money.
I think that this is a WordPress problem, because many WordPress users will receive these emails and feel that their site is insecure. If WordPress thinks longterm, this is very problematic.