Redirection from an HTTP connection to a "data:" URL assigns the referring site's origin to the "data:" URL in some circumstances. This can result in same-origin violations against a domain if it loads resources from malicious sites. Cross-origin setting of cookies has been demonstrated without the ability to read them. Note: This issue only affects Firefox 49 and 50. This vulnerability affects Firefox < 50.0.1.
https://www.mozilla.org/security/advisories/mfsa2016-91/