Final comment! In the end the reason for the whole problem was a faulty Addon in my Firefox browser (Version 60.0.1 64 Bit in Win 7 64 Bit). Addon name: Web MIDI API Version 18.104.22.168.
Sorry, to have bothered you but I was quite upset. The true reason for the described strange behaviour is NOT the default system template script but a somewhat corrupt installation of the CKEditorPlugin! I disabled this editor and switched over to the old fckphplist editor and - voila! Everything looks and works again as you would expect. I do not know what is wrong with my installation of the CKEditor Plugin but may be when I have calmed down I can repair it. So the night is over and I learned somthing. Good bye.
this contribution is a little embarrissing. I can not really believe what i saw in the code. It is so rediculous that it may be somehow a local error on my machine or what else.
Nevertheless I re-installel phplist twice and then on another domain of mine completely new and the same result. Can you tell me what YOU see after an automated install ?
I added the default system template to the system as is intented and automated by just pressing one knob. Then I opened the template and switched to pure html code. There appeared a very very very long code for this tiny template AND this code consists almost exclusively of MIDI code, Right, code for a MIDI controller (Note on, Note off, etc.) many lines which you usually use for controlling musical gear. How can that happen? Ok, I occasinally work which such gear but never mingel code like this. And as I told I installed thrice and have to assume that this code is not mine. Can you please check this and tell me if I am going crazy?
I assume now that the creation of the system template by using the ‘defaultsystemtemplate.php’ in the admin directory interferes with some files (of the same name?) on my computer and thus unintended mingling of code is happening. So this might really be a local phenomenon. however, it should not happen. (phplist 3.3.1 to 3.3.3 was used. Can send this crazy code as I now assume you will not find it on your computer. Regards
Edit2: It is a true bug! In my fourth new installation the same phenomenon happened. When creating the default system template (dst) a lot of midi code supposedly from somewhere on my computer is added (…>/script>). I can delete this code completely and copy the raw true code from the defaultsystemtemplate.php and save it. This results in a surface as you would expect from the dst. But when you open up the html code all the useless MIDI code is there again. The same is true when you create a new template - same procedure - same result. Can you help me? I do not like to sent a lot of useless code to my subscribers. Though I do not know if this code is sent. Test mail code is confusing for me but do not detect the MIDI… Oh, what a mess… Regards, Rainer