They don't seem to know or care what is going on with their own email systems.
What’s described sounds like it might be spooky. It might also be a magic trick to some degree… Mr. Cox’s PoC—“I gave a fresh Hide-My-Email alias to a guy who knows who I am, and he told me the email on my Apple ID”—is consistent with the claimed behavior but not exactly watertight.
It also sounds like it might be the sort of thing that’s either “just how the email ecosystem works” or mitigable by covert means. For example, if Apple can identify exploit attempts from its privileged vantage over its infrastructure, maybe that’s the basis for its relaxed impact assessment.
I’m reminded of Amazon’s risk assessment with respect to some Quick bug recently [0]: “yeah, it’s bad, but we checked and there are literally zero people other than you who’ve ever used that feature that way.”
Or maybe it’s the kind of thing that requires a structural sort of tradeoff to conclusively fix. I could imagine the exposure mechanism having something to do with their forthcoming move to segregate aliases to their own “private.icloud.com” domain.
(A move at which Mr. Cox swipes in the 404 Media article, too, of course, but hey—“impact journalism.”)
And then, since we have only vibes to go on, there’s the judgment reflected in the researcher’s email to Apple:
> “It seems that ending new sales of Hide My Email until the problem is fixed would be an effective way to limit the number of customers at risk. Is that an option?” Murphy wrote back.
I can only hope that was a sardonic moment of frustration quoted out of context… Hide My Email is “sold” as a tiny tiny bonus feature of a much bigger iCloud+ product. But as-quoted, it’s giving a little bit of Chicken Little… I’m reminded of the time somebody demanded that a firm I’m familiar with halt all sales (and pay hush money) because of a CRITICAL SECURITY HOLE: you could access the contents of a password field by typing the password in the field, pressing F12 in the browser, and typing $(“#pw-input”).value …
If the flaw really is the sort of thing that required fundamental product changes to fully address—like this domain segregation thing—a year doesn’t seem wild at all to make that transition safely and at scale. Especially if they identified effective mitigations in the meantime.
Then again, maybe they really are negligent…
[0] https://www.theregister.com/columnists/2026/05/13/aws-patche...
Can you also clarify whether it matters what the forwarding address is? e.g. whether my HME addresses forward to an icloud.com address (e.g. js2@icloud.com) or say a personal domain associated with my Apple ID (e.g. js2@example.org).
To me it seems, at least in this instance there is not even an exploit needed and the feature apparently is just broken beyond belief.
Apple is about to make Hide My Email useless
Send it to the USA media and regulator too
Do you believe the mitigation would be difficult to engineer? If, say somebody else, publicly disclosed the unmasking technique how long would you guess it would take Apple to implement a verifiable fix?
I am guessing you haven't tried that excuse on the users your witholding is leaving exposed.
> It reveals the email linked to the Apple ID.
So I assume you are right that it has nothing to do with the email itself, but prob some other service that links the obfuscated email to the appleid of the user.
[0] https://www.404media.co/apple-hide-my-email-vulnerability-re...
I don't know what I am doing, but from a quick test, the mail header is at least disclosing the internal recipient (mail@host.com) "translation address" (as mail_at_host_com_12345abc_12345abc@icloud.com) and an alias creation date. But the latter seems to be a unix timestamp related to the real address alias creation time and is identical between an hidemyemail mail and a normal one, so there may be already a possible information leak for correlation. Side note, it also seems like the sending hidemyemail server contains the unsuspicious name "junk_forwarder". Lol.
Disclosing an address as alias and particularly as throwaway alias (through the translation address and server) already seems kinda counterproductive to begin with, but I would bet you can use this information somehow to get the sender "translation address". Either by some API interaction, or by messing with the mail header scrubbing of the translation service somehow. A server named "junk_forwarder" may be a little more lenient about what to accept or not.
Edit: Can confirm the Reddit comment linked. You simply send an email to the HME address, reply from Apple mail client, and then the real mail address gets disclosed. Mind you not even hidden. It's shown as sending from the HME alias in mail, but I received the mail with the real address as sender......... Jesus fucking christ, Apple. Did you even test this a little?
> we will not discuss or disclose the details of the exploits until they're fixed.
But if there's a public forum where the cat's already out of the bag, then game on. Perhaps this:
https://www.reddit.com/r/apple/comments/1ukilw1/apple_hide_m...
...which makes it seem like perhaps the attack surface is limited to scenarios involving a Yahoo/Sonic address (assuming that Apple only sends X-Sonic-* headers when talking to those providers that want to see it), which might be a small percentage of users.
> I can only hope that was a sardonic moment of frustration quoted out of context
I didn't make my point clearly there, and I think it makes more sense in context, but it was a sincere suggestion that Apple could stop allowing new people to use Hide My Email. There are many other email aliasing services, so they wouldn't be depriving people of a unique offering. At the time, I wasn't aware that Hide My Email was only available as part of iCloud+. All I knew was that it wasn't free.
> We hope that Apple will take steps to limit the attack surface area even before the vulnerability is fixed. Disabling creation of new Hide My Email addresses could be helpful. It also seems responsible to notify all Hide My Email users of the risk.
Thank you for your work, and your persistence against our Sphinx-like overlords!
Now if only I had a better client on my phone (never buying an iPhone again)
If you setup HME to forward to a non-iCloud address, you absolutely risk leaking information if you reply to an HME email. For example, in my testing, the replies disclosed the DMARC policy I have on my domain when Apple's SMTP servers themselves added that header:
X-DMARC-Info: pass=pass; dmarc-policy=reject; s=r1; d=r1; pdomain=mydomain.org
So in that sense, I'm agreeing with you.
But, that's not the claim that alexpc201 made. To wit: "sends a response email (from the real address) with the rejected email message"
Sure, that's possible, but I doubt it and I was also unable to trigger such behavior. An oversized message is bounced directly by the receiving SMTP server with:
message size 67539976 exceeds size limit 28311552 of
server mx01.mail.icloud.com[17.57.154.33]
Reporting-MTA: dns; mailfout.phl.internal
X-Postfix-Queue-ID: 13B6AEC00E7
X-Postfix-Sender: rfc822; elided@pobox.com
Arrival-Date: Thu, 2 Jul 2026 18:28:38 -0400 (EDT)
Final-Recipient: rfc822; word-word.0x@icloud.com
Original-Recipient: rfc822;word-word.0x@icloud.com
Action: failed
Status: 5.0.0
Remote-MTA: dns; mx02.mail.icloud.com
Diagnostic-Code: smtp; 550 We are unable to send your email as one or more of its attachments may be corrupted or may contain malicious content.
Elsewhere in this thread someone theorized that the leak doesn't involve SMTP at all, but maybe some other service Apple operates.
---
Since doing this testing, I updated my HME setting to forward to my real iCloud.com address instead of my personal domain. If I then reply on icloud.com, nothing that I can see is leaked.
So basically, the HME SMTP servers are:
1. Rewriting the From and To address in a reply.
2. Are not sanitizing message headers.
3. When replying from a non-icloud.com domain, are actually inserting new headers which leak information such as your domain if you have a DMARC policy setup.
Eeek! So be careful when replying to an HME email! But even though the blog post is vague, I believe the claim is that no reply from the HME address is necessary.
> So the theory now has to be that possible to sneak something past the edge SMTP server, past the point where the system rewrites the HME address, then bouncing, and in sending the bounce, failing to properly rewrite something on the way back out, thus disclosing the real address. I remain skeptical that's what's happening.
Try figuring out the message size that the forwarding edge (icloud.com) accepts, but the receiver (the mailbox server) does not. SMTP is tricky business, because you don't really know at which point the NDR might happen.
Is this a theory or did you test this yourself?
Anything even 1 byte less than that rejected at the edge passes through. And there's not a chain of SMTP servers either. It goes through a single SMTP server into my iCloud mailbox.
If you think this is the flaw, you're welcome to prove it. I'm skeptical and not spending more time on it.
Edit: this is with forwarding to an icloud.com address. If forwarding to a private domain and that domain's SMTP servers have more restrictive size limits, then yes, that bounce could reveal the real address. Don't use a non-icloud.com real address with HME. But the original (vague) description of the problem says nothing about whether the real address matters. In any case, I have no way to test that scenario.
Does the initial sender matter? Like if it’s the HME address that sends first and receives the reply? I have around 180 of these addresses.
It's not just in the source, I totally overlooked the fact the real email address is shown as sender. Lol.
> Does the initial sender matter? Like if it’s the HME address that sends first and receives the reply? I have around 180 of these addresses.
Appears so. Here is exactly what I did:
1. Created the HME through mail, sending to other email service address (OMA). (This disclosed the information in my original comment.)
2. Did some reply ping pong. (No additional disclosure.)
3. Send a new email from OMA to above HME.
4. Replied from iOS mail client (UI showing usage of HME alias. Yes, I verified this multiple times not to make a fool of myself.)
5. Received at OMA, the real address is disclosed.
6. On the iOS client side, the mail shows up as sent from the real mail address, too.
Not sure if 1. for HME creation is required, you can likely skip straight to 3. for any HME address.
Funny enough, I observed 6. in the wild before, but was kinda hoping that's an artifact of forwarding a copy of the mail to the thread. I tested this some, but not this particular ping-pong. So yeah... I now gonna check where I evidently leaked my real mail address already...
#5., real address not disclosed at OMA for me.
(now that I see the reddit thread) is this potentially Yahoo/Sonic-only?
What is bad UX is the fact there are two reply buttons in the iOS client. One "in" the mail and one for the thread. The mail one pretends to reply from HME alias, the thread one does not. This alone could expose you by accident, since anyone would expect to reply with HME in any case, but you get exposed either way.
The disclosure mail has this in source (from OMA perspective):
X-Icloud-Hme: p=HME@icloud.com; d=; f=REAL@icloud.com; r=to; e=OMA@OMA.COM; s=OMA@OMA.COM
I know little about mail, but I think it's pretty evident there is a fuck-up, because the HME and real mail address should never be found next to each other anywhere. I kinda suspect this is meant to be forwarded to the sent box like this, but got forwarded to OMA or something.
Again, I checked multiple times, the iOS mail client shows the HME in from-field. It could be, this is "just" a bug in the iOS mail client. I presume the OP found something generally wrong with HME. But only the abyss I see here makes me absolutely not trust Apple with this anymore.
Did you do 2. and to the same OMA? The thing is, initiated from from iOS client, the ping pong goes fine-ish (despite disclosing HME usage) first time, but then "reusing" the alias, exchange initiated from same OMA is the important differentiation, apparently. There must be some issue with header rewriting, threading, idk... I presume OMA structures the header differently and does not trigger HME response as Apple expects. Or Apple already got a HME translation route for the OMA, and can't make a new one, fails to reuse the old one. Some mail servers may cut some X-whatever meta data. I mean, "X-Mailer: iPhone Mail" is cringe as fuck bloat...
Using Mail: Version 16.0 (3864.600.51.1.1).
Sent from a Google Apps mail.
I'm not actually doubting it. saagarjha knows his stuff. I just don't see it, so maybe I'm holding it wrong.
> The reason why my IP address is visible is because Apple Mail sends emails with SMTP.
Unless you use a proxy, your IP address is visible to an SMTP server, just like it's visible to an HTTP server when you use a web browser. This is not specific to Apple Mail or to Gmail.
Nevertheless, as js2 said in another comment, it’s your mail provider (in this case Gmail) deciding whether to include the sender’s IP address or not.
This is just a pointer for exercise you could do if you are interested. I can’t tell what is the actual HME vulnerability they claim to exist.
I would need to test with my hosting Webmail client, so maybe tomorrow.
Have you tried a VPN? I wonder, if Apple manages to expose IP despite a VPN. They had issues with stuff like that before.
I’ll mess around, today, and see what comes up.
I think that's common among email providers.