If cursor visibility is toggled by script using from 'none' to an image and back through script, the cursor will be rendered temporarily invisible within Firefox. Note: This vulnerability only affects OS X. Other operating systems are not affected. This vulnerability affects Firefox < 58.
https://www.mozilla.org/security/advisories/mfsa2018-02/
https://bugzilla.mozilla.org/show_bug.cgi?id=1423275