I have an active account at ebay-kleinanzeigen.de (like Craigslist in the US).

Today I got a valid email from them that my email address was changed.

On my mac, I opened up my ebay-kleinanzeigen account in my Chrome browser and was logged in with the hacker's email address.

I understand how the attacker could have cracked the password and change my email address in the account. Once you have access to the ebay-kleinanzeigen account, changing the email address is just two clicks. But how could I had been logged in with his address in my own browser?

I also recently turned on a very old Windows 7 machine and logged into my Google account. Hence the question if the attacker compromised my browser and the login could have been synced across the browsers of the different machines?

What is the most probable scenario and what are my next steps?

  • 1
    I suggest contacting eBay and explaining the situation to them. I don't know if the support 2FA, but if they do, I highly recommend enabling it.
    – MechMK1
    Sep 30 '19 at 8:18
  • I think they don't support 2FA Sep 30 '19 at 8:22
  • @tungsten can the login be synced between browsers of the different machine? Otherwise the only explanation for me would be that my MacBook was compromised. Sep 30 '19 at 8:24
  • @MechMK1 Also the ebay-kleinanzeigen account is not an issue. As I was already logged in with the hacker's account, I changed the password and the email address again to my old email address. Sep 30 '19 at 8:30
  • Most porbably scenario would be that ebay-kleinanzeigen.de doesn't probably kill all sessions on password / email change so you're still connected to your account.
    – Xavier59
    Sep 30 '19 at 11:23

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