If you run Firefox as your browser, you should update it ASAP if you’re running anything less than version 58.0.1 because of an exploit that the Cisco security team found:
A vulnerability in Mozilla Firefox could allow an unauthenticated, remote attacker to execute arbitrary code on a targeted system.
The vulnerability is due to insufficient sanitization of HTML fragments in chrome-privileged documents by the affected software. An attacker could exploit the vulnerability by persuading a user to access a link or file that submits malicious input to the affected software. A successful exploit could allow the attacker to execute arbitrary code with the privileges of the user. If the user has elevated privileges, the attacker could compromise the system completely.
Mozilla has confirmed the vulnerability and released software updates.
In English, that means that an attacker can pwn you if you run Firefox on a computer with administrative rights. And by pwn I mean that they can literally do anything they want. So to avoid pwnage, make sure you’re running the latest Firefox. Do it now. You’ll thank me later.