Firefox could be made to crash or run programs as your login if it opened a malicious website.
Multiple security issues were discovered in Firefox. If a user were tricked in to opening a specially crafted website, an attacker could potentially exploit these to cause a denial of service, bypass same-origin restritions, or execute arbitrary code. (CVE-2018-12405, CVE-2018-12406, CVE-2018-12407, CVE-2018-17466, CVE-2018-18492, CVE-2018-18493, CVE-2018-18494, CVE-2018-18498)
11 December 2018
A security issue affects these releases of Ubuntu and its derivatives:
Firefox could be made to crash or run programs as your login if it opened a malicious website.
Multiple security issues were discovered in Firefox. If a user were tricked in to opening a specially crafted website, an attacker could potentially exploit these to cause a denial of service, bypass same-origin restritions, or execute arbitrary code. (CVE-2018-12405, CVE-2018-12406, CVE-2018-12407, CVE-2018-17466, CVE-2018-18492, CVE-2018-18493, CVE-2018-18494, CVE-2018-18498)
Multiple security issues were discovered in WebExtensions. If a user were tricked in to installing a specially crafted extension, an attacker could potentially exploit these to open privileged pages, or bypass other security restrictions. (CVE-2018-18495, CVE-2018-18497)
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
After a standard system update you need to restart Firefox to make all the necessary changes.