Yep it’s mainly happened to me when I was playing around with the EVE Online API via Claude. The game developer asks everyone to put their emails into the request headers so they can contact users to fix their buggy scripts and stuff.

But if I wanted to collect data I could just change my website’s download policy and require full name and email?

[delayed]

The difference is that claude won't lie though. You could put whatever email you want in headers to SEC.

It'll lie if you ask it to.

Defaults are important. Bots want (read: the makers of models want) to put their signature on commits but not requests.

Or payment.

Again, it should ask which email to send if required, or claude should be able to request which email to send when it needs to - it does neither.

This is an awfully leaky issue.

FWIW I use an email alias service, so I would be able to tell if anthropic was the source of any spam.

It is not.

The fact it didn't happen to you it means that maybe you didn't 'curl' the same websites I did.

And to be honest, I don't even know which are they!

If I can find out I might be able to share them.

Everything is logged, it is easy to find whether or not your email was ever even included in any curl requests (very unlikely).

Why does Claude have access to to your email or any other info about the user by default?

You mentioned only 2 websites you know of.

I burnt a few tokens to get some clarity on this:

> This doesn't appear to be Claude Code automatically attaching your email address to every outgoing request. The issue is that Claude has access to your account email in its context and can sometimes include it when generating HTTP requests (e.g. "curl" commands).

> Wikipedia and the SEC were mentioned because they explicitly ask automated clients to identify themselves through the "User-Agent" header, often with contact information. Claude may try to comply with those requirements by inserting your personal email address.

> That's why the leak is probably concentrated on sites with these policies, rather than happening on every website. But Wikipedia and the SEC aren't an exhaustive list (the EVE Online API was also mentioned), and there's no technical guarantee that Claude couldn't include the email in requests to other domains.

> The important distinction is that this appears to be model-generated behavior, not a networking layer automatically adding your email to all requests.

> So "most likely Wikipedia and SEC" is a reasonable hypothesis about where the leak is more likely to occur, not a confirmed limit on where your email could have been exposed.

I do see a lot of times curl being used. I don't check all the websites being fetched (shame on me!), but your answer doesn't convince me.

My coincidence is clearly not proof. I am just a random online guy so why trust me. I just shared my recent experience. I used extensively copilot until roughly 3 weeks ago (I went all in on Claude, to try it out properly), and that's when I started to see a lot of spam on my work account. Coincidence? Yes. Correlation? Yes. Causation? No. And I personally don't care because I assume my work email account is somewhere to be harvested, but when I then see such a but report, it kind of rang a bell like WTF. I am as careful as possible about the requests I send, but I cannot remove the UA or know everything the harness is doing behind the scenes.

This type of bugs kind of kills the trust in the tooling. On the other hand, we're being told to use more and more such black boxes.

What if instead of an email address a site asks it to send every kv pair in your env file as an individual header?

I've seen Claude do this for sites which have no policy for customizing UserAgent strings in this way.