There are various ways to "not leave it open" remove it, pin it, comment it out, maybe you should read more documentation before using it. EG: 1st>https://wiki.debian.org/DontBreakDebian
All though deb-multimedia is not listed, it should be. But it could be considered a "random website". As a newbie, you should just stay with the Debian repositories until you have a better understanding of the packaging system, etc.
In all the years I have been using Debian, I have never needed these "deb-multimedia", or any other random websites, and do not use them. Recently I did download some, from somewhere, to try to test and trouble shoot for some one , but the results were the same, "Best to just not use them!", Others will disagree, and some will tell you they are ok, ...the only secure way to decide is using your own experience,and learning about the "Debian way"
, |||https://wiki.debian.org/DontBreakDebian ... bad_advice
Don't blindly follow bad advice
Unfortunately there's a lot of bad advice on the Internet. Tutorials found on blogs, forums and other sites often include instructions that will break your system in subtle ways. Don't simply follow the first advice you find, or the tutorial that seems the easiest. Spend some time reading the documentation and compare the difference between tutorials.
It's better to take the time to figure out the correct way to do something first than spending even more time fixing a broken system later. You would not let some random stranger feed your baby; do not execute commands without first understanding what they do.
Blog and forum posts don't expire. Instructions that might have been safe a couple of years ago might not be safe to follow any more. When in doubt keep researching and read your version's documentation.
by Bagger » Although I had to add the deb.multmedia to the sources list, to be able to get the latest version of kodi.
I can see you are one of these,> https://wiki.debian.org/DontBreakDebian ... f_Syndrome
"Must have the newest",just does things randomly , with out thinking or reading anything , all ways in a hurry, etc,...so guess I just wasted time here, ...You don't really need the latest version of kodi, but then you probably also think you still need MS windows, ....maybe ask Bester69,
he will be happy to mislead you and give you bad advice.
Oh, and side note: When your system is broken and you need help fixing it, be sure to start the topic somewhere else:
Docs, Howtos, Tips & Tricks
Share your own howto's etc. Not for support questions!