Requirements ngrok Before patch (to reproduce the problem). It's enough to do it just with 1 branch. Create, using your favorite tool (mdk...) a new site (mysql). run ngrok http 80 and annotate the "Forwarding" url (the http one). Once it's installed, edit config.php and set: $CFG->prefix to "pre_" (instead of "mdl_" ). $CFG->wwwroot to the url annotated in the previous point. (it should look like this, but with the values commented above) $CFG->prefix = 'abc_'; $CFG->wwwroot = 'http://60c21ab8f6df.ngrok.io/path/to/site'; Save changes. Point your browser to the site URL. Verify that you see the "Copyright notice" page. Click continue. Verify that you see the "Server checks" page. Click continue. Verify that all the installation happens (it's a long process). At the end, click continue. Verify that you get the "Installation must be finished from the original IP address, sorry." error page (this is the problem being fixed here). After patch (to verify the problem is solved). To be done with all branches (35, 37, 38, 39 and master). Repeat steps 1-7 above, you only need to change the $CFG->prefix value to a different one for every branch (for example "m35_", "m36_"... and so on). Verify that you see the page where the admin details (username, pass...) are introduced, not the error one in step #8 above.