What are the ways to know if a vendor ever suffered from a data breach?

I came across this - https://en.wikipedia.org/wiki/List_of_data_breaches

But this seems incomplete, for example, this salesforce breach is not reported: https://lawstreetmedia.com/tech/salesforce-cloud-data-breach... And so Is this mailgun breach: https://www.zdnet.com/article/mailgun-hacked-part-of-massive...

So I am wondering if there is a more reliable source that aggregates all that?

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