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jecilop - this thread might help do what you want ==>>
Censorship - How to Censor ebooks
Don't bother reading past the first post, the replies add nothing useful.
Added : A nice way to implement this might be as a viewer plug-in. It would highlight all occurrences of words in a user supplied list. Toxaris has recently done this (at my request) in his Epub Tools addin for Word.
I don't know if the new browser based viewer will support plugins, nor if existing viewer plugins will be reusable (perhaps with some tweaks).
BR