Mozilla · Firefox · CVE-2017-7783
**Name of the Vulnerable Software and Affected Versions**
Firefox versions prior to 55
**Description**
The issue occurs when a long user name is used in a username/password combination in a site URL, causing the resulting modal prompt to hang in a non-responsive state or crash. This results in a denial of service.
**Recommendations**
For versions prior to 55, update to version 55 or later to resolve the issue.