Ubuntu Security Notice 4717-2 - USN-4717-1 fixed vulnerabilities in Firefox. The update caused a startup hang in some circumstances. This update fixes the problem. 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, obtain sensitive information, conduct clickjacking attacks, or execute arbitrary code. Various other issues were also addressed.