In Moodle, the cookie can have a prefix. If one is set, the session sent to SEB server is not correct.

[lucaboesch]

This issue duplicates the one for SEB Windows, https://github.com/SafeExamBrowser/seb-win-refactoring/issues/848. The mechanism getting the user ID for Shibolleth authenticated Moodle users should fetch /mod/quiz/accessrule/sebserver/classes/external/user.php of if that isn't around, /theme/boost_ethz/sebuser.php and get those addresses providing a Session cookie. The session cookie can have a variable name and isn't always "MoodleSession", but can vary. Refer to https://github.com/SafeExamBrowser/seb-win-refactoring/blob/master/SafeExamBrowser.Browser/Handlers/ResourceHandler.cs to see how it is dealt with in SEB Windows. Thanks.