If an image had not loaded correctly (such as when it is not actually an image), it could be dragged and dropped cross-domain, resulting in a cross-origin information leak. This vulnerability affects Firefox < 71.
Exploitability
AV:NAC:LPR:NUI:RScope
S:CImpact
C:HI:NA:N7.4/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N