The generation thread uses a single request to generate all the contents / pages needed.
But the if the pipeline used to generate a content (or a page) doesn't pop the current CMSContext or if it doesn't push on new CMSContext in the CMSContentHandler, it will retrieve the preceding content's context because it is never removed.

Generation pipelines usually push a new CMSContext so this should never happen but if someone forgets to push a context, instead of failing because of a NPE, the generation will end normally and a page can be generated with the content of another page.