Pretty sure the footer is just some velocity/soy template so you would need to replace that template file specifically in the installation directory. Your plugin can only really apply some web resources but it probably cannot prevent any "leakage" from somebody who knows what they're doing.
And also - Jira version is present in page source on several pages. So even if you did hide it from the footer, it would still be visible in page sources. It's also not that difficult to judge the Jira version if you know what you're doing and what you can expect from the different versions (well, maybe not exactly but.. roughly, roughly).
This page covers both the page markup and footer: https://confluence.atlassian.com/jirakb/hiding-the-jira-version-number-from-page-markup-1056673381.html
But again though, I don't think there's a different direction than modifying those files - you could try to obfuscate it from a plugin, but that will not prevent Jira from already sending out that information.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.