From Monkey Island wiki
If you feel that a page has been comprehensively vandalized follow this procedure:
- Go to page history (click the link at the top).
- If the vandalism is recent click the undo-link next to the current version of the page.
- You will be presented with a summary of the edits done on the page by the previous user and a sandbox displaying the code with the edits removed.
- Click save page.
The same can be achieved by opening a previous version of a page from page history, opening it with edit and saving.
If vandalism is local and only present in one part of an article it can be removed through simple editing. However, in a longer article it's better to make sure by quickly reading through the page in case vandalism is further implemented. If you want to save time go to the history section and view the comparison to the previous version of the article.