A security issue has been found in Firefox < 54.0 and Thunderbird < 52.2, where characters from the "Canadian Syllabics" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of being rendered as their raw "punycode" form, allowing for domain name spoofing attacks through character confusion. The current Unicode standard allows characters from "Aspirational Use Scripts" such as Canadian Syllabics to be mixed with Latin characters in the "moderately restrictive" IDN profile. Firefox and Thunderbird behavior has been changed to match the upcoming Unicode version 10.0 which removes this category and treats them as "Limited Use Scripts."
A security issue has been found in Firefox < 54.0 and Thunderbird < 52.2, where characters from the "Canadian Syllabics" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of being rendered as their raw "punycode" form, allowing for domain name spoofing attacks through character confusion. The current Unicode standard allows characters from "Aspirational Use Scripts" such as Canadian Syllabics to be mixed with Latin characters in the "moderately restrictive" IDN profile. Firefox and Thunderbird behavior has been changed to match the upcoming Unicode version 10.0 which removes this category and treats them as "Limited Use Scripts."
https://www.mozilla.org/en-US/security/advisories/mfsa2017-15/#CVE-2017-7764 https://bugzilla.mozilla.org/show_bug.cgi?id=1364283 http://www.unicode.org/reports/tr31/tr31-26.html#Aspirational_Use_Scripts
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