5 ms·

What can you do to prevent automatic confirmation in that case?

sandermvanvliet 2y ago
As far as I know there’s nothing. The alternative is to send an OTP in the mail and tell the user to enter that. In that way there is no link to auto confirm. However, if you do that ensure that you have a way to jump straight to the page to enter the OTP because (looking at you Samsung) the account registration process can expire or the app is closed (not active long enough) and your user is stuck
miohtama 2y ago
The link leads to a page where you need to press a button (HTTP POST).
mixedbit 2y ago
I run an authorization service that allows to log-in using magic links and we managed to solve this. First approach was for the link opening GET request to do not log the user in, but to include an HTML page with JavaScript that issued a POST request with a code from the link to log the user in. This worked well for a long time, because email scanners were fetching links from emails with GET requests but did not execute JavaScript on the fetched pages. Unfortunately, some time ago Microsoft tools indeed started to render the fetched pages and execute JavaScript on them which broke the links. What works now is to check if the link is open in the same browser that requested the link (you can use a cookie to do it) and only automatically login the user in these cases. If a link is open in a different browser, show an additional button ('Login as <email address>') that the user needs to click to finish the login action. MS tools render the login page but do not click buttons on it. The issue that MS tools introduced is broader, because it affects also email confirmation flows during signups. This is less visible, because usually the scanners will confirm emails that the user would like to confirm anyway. But without additional protection steps, the users can be signed up for services that they didn't request and MS tools will automatically confirm such signups.
- szszrk 2y ago
  > check if the link is open in the same browser that requested the link (you can use a cookie to do it) and only automatically login the user in these cases. If a link is open in a different browser, show an additional button ('Login as <email address>') that the user needs to click to finish the login action. Thanks for checking if it's the same browser. Some companies don't care about that (cough booking cough) so harmful actors just spam users with login attempts in hope a user will click by accident. And puff, random guy gets full access to your account. I got those every day, if I ever needed to login this way I would not be able to figure out which request is mine.
  - vanviegen 2y ago
    Wouldn't that just log you in on the browser doing the clicking, instead of the attackers browser?
    - szszrk 2y ago
      You mean in the booking example? They logged in the browser that... requested access. So basically anyone that knew your login/email. I think it should check if browser requesting is the same as the one confirming, or just drop that whole dumb mechanism entirely.
- keskival 2y ago
  Ok, what if an email has "click this link if it was you who tried to log-in", or "if it wasn't you"? Will Microsoft automatically authenticate malicious actors, or block yourself from services built with assumptions that the email client won't auto-click everything?
  - mixedbit 2y ago
    Login links from my service were automatically clicked and rendered and I know that other services discovered similar problems. Based on this I think that it is very likely the case with all the links in emails, but I don't know if there is any additional heuristic involved that would treat some links differently. See also this issue which suggests that all links are opened: https://techcommunity.microsoft.com/discussions/microsoftdefenderforoffice365/possible-major-problem-with-ms-defender-scanningclicking-links/3874918 https://techcommunity.microsoft.com/discussions/microsoftdef... Note that this doesn't affect all Outlook users, this Microsoft Defender for Office 365 is a separate product that only some companies use.

As far as I know there’s nothing. The alternative is to send an OTP in the mail and tell the user to enter that. In that way there is no link to auto confirm. However, if you do that ensure that you have a way to jump straight to the page to enter the OTP because (looking at you Samsung) the account registration process can expire or the app is closed (not active long enough) and your user is stuck

miohtama 2y ago

The link leads to a page where you need to press a button (HTTP POST).

mixedbit 2y ago

I run an authorization service that allows to log-in using magic links and we managed to solve this. First approach was for the link opening GET request to do not log the user in, but to include an HTML page with JavaScript that issued a POST request with a code from the link to log the user in. This worked well for a long time, because email scanners were fetching links from emails with GET requests but did not execute JavaScript on the fetched pages. Unfortunately, some time ago Microsoft tools indeed started to render the fetched pages and execute JavaScript on them which broke the links. What works now is to check if the link is open in the same browser that requested the link (you can use a cookie to do it) and only automatically login the user in these cases. If a link is open in a different browser, show an additional button ('Login as <email address>') that the user needs to click to finish the login action. MS tools render the login page but do not click buttons on it. The issue that MS tools introduced is broader, because it affects also email confirmation flows during signups. This is less visible, because usually the scanners will confirm emails that the user would like to confirm anyway. But without additional protection steps, the users can be signed up for services that they didn't request and MS tools will automatically confirm such signups.

szszrk 2y ago
> check if the link is open in the same browser that requested the link (you can use a cookie to do it) and only automatically login the user in these cases. If a link is open in a different browser, show an additional button ('Login as <email address>') that the user needs to click to finish the login action. Thanks for checking if it's the same browser. Some companies don't care about that (cough booking cough) so harmful actors just spam users with login attempts in hope a user will click by accident. And puff, random guy gets full access to your account. I got those every day, if I ever needed to login this way I would not be able to figure out which request is mine.
- vanviegen 2y ago
  Wouldn't that just log you in on the browser doing the clicking, instead of the attackers browser?
  - szszrk 2y ago
    You mean in the booking example? They logged in the browser that... requested access. So basically anyone that knew your login/email. I think it should check if browser requesting is the same as the one confirming, or just drop that whole dumb mechanism entirely.
keskival 2y ago
Ok, what if an email has "click this link if it was you who tried to log-in", or "if it wasn't you"? Will Microsoft automatically authenticate malicious actors, or block yourself from services built with assumptions that the email client won't auto-click everything?
- mixedbit 2y ago
  Login links from my service were automatically clicked and rendered and I know that other services discovered similar problems. Based on this I think that it is very likely the case with all the links in emails, but I don't know if there is any additional heuristic involved that would treat some links differently. See also this issue which suggests that all links are opened: https://techcommunity.microsoft.com/discussions/microsoftdefenderforoffice365/possible-major-problem-with-ms-defender-scanningclicking-links/3874918 https://techcommunity.microsoft.com/discussions/microsoftdef... Note that this doesn't affect all Outlook users, this Microsoft Defender for Office 365 is a separate product that only some companies use.