A security researcher demonstrated a new proof-of-concept attack against the latest version of Firefox by leveraging a 17-year-old known issue in the browser. The attack takes advantage of the way Firefox implements Same Origin Policy (SOP) for the “file://” scheme URI (Uniform Resource Identifiers), which allows any file in a folder to get access to files in the same folder and subfolders. Mozilla responded by saying that the company has no plans to fix this issue in its browser anytime soon.
Source: https://thehackernews.com/2019/07/firefox-same-origin-policy-hacking.html