Unable to view .txt in html iframe in Firefox

(This may look like a silly question, I am sorry, its too specific but I am unable to find a solution to my problem)

While playing with some local html files, I have found that when I try to open a .txt file within an iframe in Firefox, it shows a Not Found message saying that Firefox couldn't find the file in the directory where the html file is stored.

But on opening the same html file in Chromium, everything works well and the text file is opened within the iframe.

My code for iframe is as follows:

<iframe src="file:///home/aakash/Desktop/todo.txt" width="300px" style="background-color: rgba(255, 255, 255, 0.671); border: 0cm; display: inline-block;"></iframe>

Everything works well on Windows OS on the other hand...