Given that the OP did later post that they use Yahoo and had been recently making real transactions on Vanguard, I'm almost 100% sure this was just Yahoo's incorrect AI summary added to the top of a valid Vanguard confirmation email.
A family member had this exact same Yahoo AI summary (purchase of 100 shares of Apple) added to the top of their valid Vanguard confirmation email about a month ago. That is why I recognized it immediately and originally responded to the OP to try to allay their concerns. I had found the Reddit post I linked sometime after I had helped my family member figure it out, so I knew the issue was a very common one.
It is unfortunate, that Yahoo is making valid emails look like scams, as it will end up making the scam emails more effective. Also, If people make the mistake of blocking a valid email as spam (as is often recommended for questionable emails), then they will no longer receive any confirmation emails from that company.
I can only imagine how much time Vanguard customer service has wasted responding to calls caused by these terrible AI summaries from Yahoo. I also found posts where people reported the Yahoo AI had similar hallucinations on emails from other companies with wildly incorrect quantities reported for item purchases, etc.
Yahoo's AI better save people a lot of time in the future to make up for how much of people's time they've wasted so far.