Zero-width characters pose a security risk and existential threat to ENS

[royalfork]

From an earlier draft of UTS-46, one reviewer brought up the emoji case:

7. If CheckJoiners, the label must satisfy the ContextJ rules from Appendix A, in The Unicode Code Points and Internationalized Domain Names for Applications (IDNA) [IDNA2008] , except that if EmojiVersion≠0, ZWJ characters are allowed if they are within Emoji ZWJ Sequences specified for Unicode Emoji Version=EmojiVersion.

Not sure if there was any additional internal Unicode discussions around this, but seems like it didn’t make it into a final draft.

@raffy

My library currently applies IDNA 2008 rules with CONTEXTJ but also retains any emoji from the recommended set and upgrades any combinations that were entered minimally-qualified.

How would it treat “.eth” vs “.eth”? Are these 2 distinct domains?