If a text string that happens to be a filename in the operating system's native format is dragged and dropped onto the addressbar the specified local file will be opened. This is contrary to policy and is what would happen if the string were the equivalent "file:" URL. This vulnerability affects Firefox < 60.
http://www.securityfocus.com/bid/104139
http://www.securitytracker.com/id/1040896
https://bugzilla.mozilla.org/show_bug.cgi?id=1435908
Source: MITRE
Published: 2018-06-11
Updated: 2018-08-03
Type: CWE-200
Base Score: 5
Vector: AV:N/AC:L/Au:N/C:P/I:N/A:N
Impact Score: 2.9
Exploitability Score: 10
Severity: MEDIUM
Base Score: 7.5
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Impact Score: 3.6
Exploitability Score: 3.9
Severity: HIGH