From mozilla.org
Mozilla Firefox could allow a remote attacker to execute arbitrary code on the system, caused by memory safety bugs within the browser engine. By persuading a victim to visit a specially-crafted Web site, a remote attacker could exploit this vulnerability using unknown attack vectors to execute arbitrary code on the vulnerable system or cause a denial of service.
source :
https://www.mozilla.org/en-US/security/advisories/mfsa2019-13/