On the latest Firefox version (69.0.1) & even before this version, i noticed that the uget-extension black listed mime types do not always work, especially with images like png/jpg/jpeg, & when i tried to investigate about that i found that sometimes the value of the file mime type is null (check the screenshot below)
So as a simple solution, i think that we could extract the file extension from the filename & use it as the mime type when this one is equal to null.
On the latest Firefox version (69.0.1) & even before this version, i noticed that the uget-extension black listed mime types do not always work, especially with images like png/jpg/jpeg, & when i tried to investigate about that i found that sometimes the value of the file mime type is null (check the screenshot below)
So as a simple solution, i think that we could extract the file extension from the filename & use it as the mime type when this one is equal to null.