Security researcher musicDespiteEverything previously reported an issue where illegal control characters were stored in as cookie values in violation of RFC6265. While fixing this issue, Mozilla developer Nicholas Hurley realized that the same issue applied to the names of cookies. These characters have now been disallowed in cookie names. This issue could result in incorrect cookie handling by web servers. External Reference: https://www.mozilla.org/security/announce/2016/mfsa2016-04.html Acknowledgements: Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges musicDespiteEverything, Nicholas Hurley as the original reporter. Statement: This issue does not affect the version of firefox and thunderbird as shipped with Red Hat Enterprise Linux 5, 6 and 7.