It seems like LibreJS, at least in Firefox, can change the expected default character coding, which I think is a bug. Here's how to reproduce:
In Firefox with disabled LibreJS I go to https://cl.lingfil.uu.se/~starback/char.html . That test only contains ------------------------------ <!DOCTYPE html> <html> <body> Lätiñ 1. </body> </html> ------------------------------ coded in Latin-1. The web server doesn't say anything about character encoding (as confirmed by wget -S) and it is shown by Firefox as the expected "Lätiñ 1.". Then I activate LibreJS and reload the page. Now it is shown as "L�ti� 1." instead, and I notice that at "View→Text Encoding" now "Unicode" is ticked instead of "Western" as it was before. It is surely good practice to always specify character encoding on the web, but the HTTP standard still specifies that iso-8859-1 is the default, so I think this should work, and LibreJS introduces a bug. (Versions: Firefox 60.5.0esr for CentOS on GNU/Linux; GNU LibreJS 7.19rc3.)
