Unwanted and unusual dialog box when opening download folder

[Moltke]

Hi everyone! Hope you're all having a nice life! I need some help here. From a couple of days ago whenever I download something and click on "open folder" in i.e Firefox download catalog, a dialog box shows asking for my password and if I do type it in it starts to update sources but folder never opens. I don't know why this is happening. Check this screenshot I took, it's in Spanish cause it's my language but it says something like:"introduce your password to perform administrative tasks. The app <</usr/scripts/update-gui'/home-moltke/Downloads>> allows you to modify essentials parts of your system".  I don't know why this is happening, so please, a little help is much appreciated. Thanks in advance for your answers!
https://imgur.com/a/52T58