Strange Formatting Issue

Hey Word Pressers,

I’ve had http://www.rapnews.co.uk running on WordPress for years.

The site is somewhat retired these days but kept live for historical purposes.

I’ve updated to the latest version of WordPress, but have started noticing big chunks of line breaks in a lot of my blog posts.

For example –

http://rapnews.co.uk/?p=1176

Looking into these pages’ html, there are lots of nasty ad code like this:

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michael kors outlet
cheap michael kors outlet
cheap michael kors

I was wondering if you could tell me how this has happened?

How can I undo all of it across each affected page?

And how can I prevent this moving forward?

Thanks so much!
Tony.