I don't understand why this problem is specific to XWikiUserSheet. Don't we have the map you mentioned for all UIXPs? I don't see why that map shouldn't be immutable for all UIXPs, i.e. prevent side effects. So why is the getExtensions() API not returning an immutable map for each returned UIX?
PS: I see that I had asked a question on WORDNOTIF-17 that didn't get noticed I think
This message was sent by Atlassian Jira (v9.3.0#930000-sha1:287aeb6)
If image attachments aren't displayed, see this article.