Bukkit

What steps will reproduce the problem?
1. A put up the sign with test
2. B use /sginedit 1 abc , left click
3. the sign changed without A's notice

What is the expected output? What do you see instead?
Don't have permission , only the owner of the sign have be changed

What version of the product are you using?

Do you have an error log of what happened?

Please provide any additional information below.

How is ownership of the sign determined? Are you using a claim/locking plugin?

3.3.4 adds an option to fire block break/place events, this should allow your locking plugins to cancel the event and prevent the line change.