We are getting reports from numerous customers that use Avast at their schools and they are reporting seeing an HTML:Microsoft-B Phish detection that is blocking their login page. This is happening on various subdomains eg https://*.tandem.co/index.php?type=login&action=form.
Can you look into this?
You can report a suspected FP (File/Website) here: https://www.avast.com/false-positive-file-form.php
Detection has been modified. Will be fixed in next update.