User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Firefox/38.0 Build ID: 20150605094246 Steps to reproduce: On at least two occasions after entering the addressees name and selecting the address with autocomplete, moving on to type the subject and message, and clicking send, I have seen the displayed address change on mouseup to one in a different address book. Actual results: The mail was sent to an unintended recipient. This resulted in data leakage and loss of privacy for myself and the intended recipient. Expected results: The mail should have been sent to the recipient selected in the address bar.

This problem was observed first in version 31.7.0 and is still present in 38.0.1. On one occasion the E-mail was a new one and on the second occasion a forwarded reply. It's difficult to offer steps to reproduce since this is a rare but potentially devastating error with unacceptable consequences breaching the Data Protection Principles and exposing me to potential prosecution. I have the messages in my sent folder, but cannot attach the headers unaltered because that would disclose private personal data. Pleas advise on how to troubleshoot further.

This is probably Bug 1152517 - Recipient autocomplete wrongly considers last mouse-hovered contact from results dropdown "selected" and then uses that unintended, random recipient upon blur (via Tab, Enter, or when moving to subject or body)

This does appear possibly related to autocomplete since entering the minimum necessary to bring up the intended recipient also brings up the substituted recipient in the same dropdown list, so it could be the selected entry was switched on send to another in the same list. However, it did not happen on Blur, but on Send - I had written the body of the mail with the originally selected address still visible. It only changed when I had clicked send, when it was too late to stop the message and correct the issue.

Well, that's blur (for the addressing area)

How can clicking send after typing the message blur the address field, when that wasn't the field in focus? I don't type the message first then go back to decide where to send it. I fill in the address first, then the subject, then type my message, then click send (or hit Ctrl+Enter). When I finished typing (in the message field) the correct address was still shown ion the address field. Then I clicked the Send button and the address changed at mouseup. Unless clicking Send momentarily moves focus to the address field, I don't see how it can blur it. This may be related, but it's not exactly the same bug because it isn't triggered by the same action.

Ok, sounds strange. Could it be some add-on causing it?

Thanks for reopening this. I have the following Extensions: British English Dictionary 1.19.1 Lightning 4.0.0.1 Theme: Default 38.0.1 Plug-ins: Shockwave Flash 11.2.202.466 (now activated only on request - which is unlikely in an e-mail) mplayerplug-in 3.50 (disabled) Next Generatiion Java Plug-in 11.45.2 (disabled) The behaviour is both strange and too rare to work out whether or how it can be reproduced. However, I know what I saw. Given that the substituted addresses on both occasions would have been in the dropdown menu produced by autocomplete, there is a pointer there to that list being still available in some form at the time I clicked send, and something must have triggered a substitution at that point. I find it odd that the list would persist so long after selection - I tend to assume once a selection has been made the list is gone and only the selected item remains, but obviously not on these occasions. If that list were actively deleted after the selection is made it would presumably prevent this substitution occurring, and the worst which could then happen is presumably that the addressee would be lost and an error generated, enabling the correct address to be entered again. It wouldn't fix whatever quirk happened, but it would limit the damage and turn a potentially dangerous privacy problem into a minor occasional nuisance, which could be investigated and found at leisure. I have not had time to examine the code, but the suggested patch for bug 1152517 suggests it is written in JavaScript within an xml wrapper.

(In reply to Magnus Melin from comment #6) > Ok, sounds strange. Could it be some add-on causing it? Marking dependent on bug 1152517 until it is proven via patch to not be related (which thankfully has a patch in development)

Is this still happening? Does it happen consistently when you send to a particular contact? Is there any relation to the other contact that is chosen on send? E.g. same email, same name, etc?

I do not know. It was a rare but worrying problem and difficult to reproduce, so it might still be able to happen, but I have no way to find out unless it happens again. I have not observed it since reporting it, but it could still be present.

Thanks for the update. Proving something is gone can be difficult. Given you haven't seen this in 7 months and no one else cc the bug or reported the same bug, it seems reasonable to close this WFM. If you see it again, definitely repopen the bug report.