I've been a volunteer host on Couchsurfing.org for 16 months. Despite the ongoing controversies surrounding the site's changes in recent years, I've always found it to be a great way to meet travelers with fascinating stories and to make new friends, not to mention a way to force a deadline upon yourself to clean up your house before the next guest arrives.
On August 15, I received an email sent from "Couchsurfing <firstname.lastname@example.org>" with the subject "Site Improvements", which read:
We have some exciting news. Find out more about the new CouchSurfing here.
The CouchSurfing team
but the hyperlink on the word "here" did nothing when I clicked on it. So I looked at the HTML source code of the message and saw that the source code of the link was: We have some exciting news. Find out more about the new CouchSu= rfing <a href=3D=E2=80=9Chttps://www.airbnb.com/signup_login=E2=80=9D> her= e </a>.
So... the email from Couchsurfing was promoting a link to their commercial arch-rival, Airbnb.
At that point I assume the message was spam that had been sent from some third-party server and simply forged a return address from couchsurfing.org, but the message headers clearly showed that the message really had been sent from Couchsurfing: Received: from messaging3.couchsurfing.com (messaging3.couchsurfing.com. [188.8.131.52]) by mx.google.com with ESMTP id v7si15118226qay.99.2014.08.15.21.30.16 for <email@example.com>; The complete message headers and message source are here.
I sent a message to Couchsurfing tech support asking if they knew what had happened, and I started a thread on the Seattle Couchsurfing page, where several other users chimed in that they had received the same email. Couchsurfing support replied to me on August 18th:
Thanks for your patience while we have been looking into this. As you saw yourself, some Couchsurfing members received an email in error on Friday night -- we apologize.
The part of Couchsurfing’s system that sends email to members was breached Friday night and an email was sent to approximately 1 million members. We take this very seriously, and we will continue to investigate and take all appropriate action until this situation is resolved.
There is no action you need to take to secure your account. Once we have further information, we will be sure to send out updates.
Then on August 19th, I received an email from Couchsurfing (presumably along with all or most other Couchsurfing users) with the subject "Incorrect email -- our apologies":
Dear Bennett Haselton:
We're writing because you may have received an odd email from Couchsurfing in the last few days titled "Site Improvements."
We apologize for any confusion this may have caused -- it should not have been sent.
-- The Couchsurfing Team
Want more details? Find them here
where the "here" link further explains: "The message was sent by an unauthorized user of our email system. No other systems were compromised, and we've addressed the circumstances that led to this unauthorized use."
So, kudos to Couchsurfing for at least alerting users that something had gone wrong. (Judging from the reactions in the thread that I started, most users who received the email simply deleted it without a second thought after seeing that the link didn't work, so Couchsurfing probably could have said nothing to their users at all, and gotten away with it. As of this writing, a Google News search for "couchsurfing hacked" turns up no other articles about the incident, so it's not as if there was a mob clamoring for answers that they had to respond to.)
On the other hand, I hope Couchsurfing is more forthcoming in the next few days about how much they know about what actually happened. When they say "We've addressed the circumstances that led to this unauthorized use," that probably means that they at least know whether the email was sent by (a) a disgruntled employee (or recently fired employee whose credentials still enabled them to access the server); or (b) someone who used an unpatched security hole to break in from the outside; or (c) something else. (I replied to the tech support ticket asking as much, but as of this writing I have not received a reply. I wasn't naive enough to think that they were probably going to tell me everything they knew, but it's one of those rituals that quasi-journalists engage in so that we can say "as of this writing I have not received a reply".)
Obviously I think it's unlikely that anyone at the real Airbnb would actually risk jail time by hacking Couchsurfing's servers to send out spam advertising the Airbnb website; it seems more like the actions of someone being snarky, possibly a former employee or an outsider with an axe to grind. Couchsurfing's apology email said "Once we have further information, we will be sure to send out updates." Hope so.