Security Specialist at IT Security Firm ESET, Mark James, commented on the issue in firefox browser. Firefox issued an update for its browser after it was discovered that a vulnerability that allows a violation of the same origin policy and injects a script into a non-privileged part of the built-in PDF Viewer. This would allow an attacker to read and steal sensitive local files on the victims computer, it could then send that data elsewhere for its own malicious use that could include identity theft, targeted phishing attacks or simply use that data for access to other private or financial websites.”]
Source: https://informationsecuritybuzz.com/articles/new-update-for-firefox-browser-exploit/