Editing Unicode (section)

==== Localised case pairs ====
For use in the [[Turkish alphabet]] and [[Azeri alphabet]], Unicode includes a separate [[dotless I|dotless lowercase {{serif|I}}]] (ı) and a [[İ|dotted uppercase {{serif|I}}]] ({{serif|İ}}). However, the usual ASCII letters are used for the lowercase dotted {{serif|I}} and the uppercase dotless {{serif|I}}, matching how they are handled in the earlier [[ISO 8859-9]]. As such, case-insensitive comparisons for those languages have to use different rules than case-insensitive comparisons for other languages using the Latin script.<ref>{{cite web |url=https://unicode.org/Public/UNIDATA/CaseFolding.txt |work=Unicode Character Database |title=Case Folding Properties |institution=[[Unicode Consortium]] |date=2023-05-12}}</ref><ref name="microsoft-case-insensitive-locale">{{cite web |url=https://learn.microsoft.com/en-us/dotnet/standard/base-types/regular-expression-options#compare-using-the-invariant-culture |title=Regular expression options § Compare using the invariant culture |work=[[.NET]] fundamentals documentation |publisher=[[Microsoft]] |date=2023-05-12}}</ref> This can have security implications if, for example, [[Code injection#Preventing Code Injection|sanitization]] code or [[access control]] relies on case-insensitive comparison.<ref name="microsoft-case-insensitive-locale"/>

By contrast, the [[ð|Icelandic eth (ð)]], the [[đ|barred D (đ)]] and the [[ɖ|retroflex D (ɖ)]], which usually{{efn|Rarely, the uppercase Icelandic eth may instead be written in an [[insular script|insular]] style (Ꝺ) with the crossbar positioned on the stem, particularly if it needs to be distinguished from the uppercase retroflex D (see [[African Reference Alphabet]]).|group=note}} look the same in uppercase (Đ), are given the opposite treatment, and encoded separately in both letter-cases (in contrast to the earlier [[ISO 6937]], which unifies the uppercase forms). Although it allows for case-insensitive comparison without needing to know the language of the text, this approach also has issues, requiring security measures relating to [[homoglyph]] attacks.<ref>{{cite web |url=https://unicode.org/Public/security/latest/confusablesSummary.txt |title=confusablesSummary.txt |work=Unicode Security Mechanisms for UTS #39 |date=2023-08-11 |institution=[[Unicode Consortium]]}}</ref>