Douglas Day's Blog

Seeker of Truth. Forever a student. Truth is at the intersection of Athens & Jerusalem.


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Every year as a HackerOne Clear verified researcher, I’m required to register on a couple of vendors that HackerOne uses. As I was going through the process of providing my social security number, 7 years of address history, my mother’s maiden name, and last bowel movement, I saw a little familiar popup in the bottom left corner:

Screen Shot 2021-07-21 at 8 03 06 AM

You know those moments when you’re trying to kick your Redbull/caffeine addiction by quitting cold turkey but you hear that familiar KSshhh sound of someone opening a can as the sweet smell of your favorite synthetic neon nectar wafts through the air? Yeah, my heart started palpitating like that.

If you’re not familiar, that little smiley square is the logo for a very popular chat widget called Intercom. This widget is commonly used by salesfolk and support engineers to assist customers. Typically, once you’ve logged in to the application Intercom uses your session to know who you are. However there’s a very important caveat with Intercom that I see misconfigured a LOT. It’s called Identity Verification. With Identity Verification, your user session in the application will provide Intercom with a hash. Without that hash, you are not able to interact with Intercom.

But the misconfiguration I see often is that Identity Verification is never actually enabled. As such, you can just tell Intercom that you’re someone else. Yes, you heard that right. For those of you missing your highschool glory days of buying jager with a fake ID, you can effectively do the same in Intercom! Minus the hangover. And the disappointed parents.

Anywho, back to the vendor! Whenever I see Intercom being used on an application, I do a quick check to see if Identity Verification is enabled. The first step to testing this is by logging in as my authenticated user and actually making a conversation:

Screen Shot 2021-07-21 at 8 38 23 AM

After a quick casual chat with the very friendly bot, I logged out and hit the login page in an incognito window, pulled up my browser’s javascript console, and ran the following to just pull up the Intercom widget

Intercom('show');

At this point, I am still unauthenticated and Intercom doesn’t know who I am. I’m effectively a guest. So I ran the following payload to trick Intercom into thinking I’m someone else:

Intercom('boot' {
  email: '<MY_EMAIL_ADDRESS>'
});

Upon refreshing the page, I noticed that the Intercom widget changed to the following:

Screen Shot 2021-07-21 at 8 43 06 AM

Aha! That See all your conversations wasn’t there before!

And yep, before you ask, after clicking that I was provided with my conversation with the support bot from before!

After chuckling for a second to myself like Ray Liotta in Goodfellas , the gravity of what I was seeing started to sink in. This was a vendor that stored my social security number, along with basically every piece of information needed to steal my identity. Yikes! I sent a quick note to the very awesome Jessica who told me to report it the the Hackerone BBP

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Always one to take an opportunity to get on Jobert’s good graces, I submitted my report later that night:

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After submitting the bug to Hackerone themselves, I went to bed content that I’d helped keep the rest of you hackers safe.

The juice gets juicier

The next day I went back to the application for fun and I noticed that a non-bot user picked up the chat and was asking me if they could help with anything. Never one to turn down some smalltalk, and wanting to see where this would lead, I responded as vaguely as I could:

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The next response surprised me…

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Whoa! Where are they going with this?!

Screen Shot 2021-07-21 at 9 10 34 AM

Lolwut. If earlier my heart was beating as fast as a redbull junkie hearing a can opening from across the room, NOW I was more like a redbull junkie hearing a can opening while simultaneously finding a crit on Redbull’s BBP. Not only could I view the support conversations and impersonate any other user, but I could also remove their security questions and set their password to summer@123.

fatality

The Resolution

After providing the new information in the H1 report, Jobert himself quickly triaged the issue and told me he’d reach out to the vendor’s CISO. After a couple of back & forths between Jobert and the CISO, CIO, and Head of Appsec, the issue was quickly patched (both the human element of changing passwords, AND the Intercom misconfiguration):

Screen Shot 2021-07-21 at 9 25 54 AM

Since you greedy hackers are wondering, no bounty was awarded as they do NOT run a BBP/VDP and awarding me a bounty would set a wrong precedent that other hackers could hunt for vulnerabilities and expect a payment. Such is the life of an ETHICAL hacker :-) Jobert gave me a nice $500 thank-you though. Thanks, bud!

All in all this was a great experience and a pretty cool story to tell. All parties involved were really rockstars here:

As always, stay safe & stay metal!

And if you like this bug: BTC to 3KvQFALzyUe27kPCBP89wMZDN9uzWHGTEU ETH to 0x462EF9726F8d68cC7A3ABedFAE62096C99E3b7A7