If you have a regular creative server without CreateYourOwnMenus installed you are fine.
If you have creative server with CreateYourOwnMenus installed then players can force op. Even if it's not used, or players don't have access to any menu you are still at risk.
If you have a survival server (or any gamemode that players do not have creative) with CreateYourOwnMenus installed, then you are fine.
I suggest you don't give players creative for 'Build Tests' or other stuff if you have CreateYourOwnMenus installed.
If CreateYourOwnMenus is not installed then you are completely fine, don't worry about this. :)
partydragen:On one of my PlayerServers I spent tons of time creating menus with every single item (But my seperate banned items) if we get up to the time that we can upload files/configs I will love if Partydragen would take out my files and I could download them and spread it out the creative servers!
The author of this plugin aswered this:
Unfortunately this is a weakness in the Minecraft server rather than something I can fix with a plugin. I reported it a long time ago, but nothing has been done, and I suspect nothing will be done.
If blacklisting commands doesn't solve it for you, all I can suggest is keeping them in survival mode but then giving them creative-like powers using other plugins, instead of full creative mode.
The Too Many Items/Not Enough Items/Just Enough Items mods can make for an excellent infinite resources front-end for creative building and all they'd need is access to the /give command to make that work on the server side. There are lots of plugins for flight in survival mode and invulnerability too.