from String to Email (which was introduced in 4.2 [1]). This shouldn't raise any issue because both types store their values in the same database table. I also added a default custom displayer for Email XClass property type that obfuscates the email address like this: [email protected] The only "issue" is that the property type doesn't change automatically when you upgrade because the XWiki.XWikiUsers class initializer (oldcore) doesn't do anything if the (email) property already exist (which is good). I'll add some comment on the release notes (5.1M1). Let me know if you think my changes could break something. Thanks, Marius [1] http://www.xwiki.org/xwiki/bin/view/ReleaseNotes/ReleaseNotesXWiki42#HNewfie...