Revision posts are saved with double-filtered content

[redsweater]

When a post is saved using wp_insert_post, the post is first sanitized with sanitize_post, which applies the content_save_pre filter to the description of the post.

Later in wp_insert_post, the pre_post_update filter is called, which causes the wp_save_post_revision method to be called, with the ALREADY-sanitized content of the post. The wp_save_post_revision ends up calling wp_insert_post for the revision entry, which this time sanitizes the post content again before saving it in the revision.

The problem here is if any content_save_pre filter (or any of the other sanitizing content filters, for that matter) produce "nonterminal" results, then the content that is saved to the revision copy ends up being an inaccurate representation of the post.

For example, the popular SyntaxHighlighter Evolved plugin:

​http://www.viper007bond.com/wordpress-plugins/syntaxhighlighter/

Uses a technique that escapes entities on the way into the database, and unescapes them on the way out. So for instance, an ampersand in the post content is escaped to "&". But by the time the post revision is saved, it is asked again to sanitize, this time converting "&" into "&".

I'm not sure what the right fix is.

[ryan]

sanitize_post() sets a "filter" field in the passed object. We can check to see if filter is already set before filtering again.

[ryan]

Check filter before sanitizing. Untested.

[ryan]

Since pre_post_update is being passed an ID instead of an object, I'm not sure how this is getting double filtered unless the global post object is being polluted and then retrieved with get_post(). I don't think that's happening here, but just in case I've put a check in get_post() to make sure it is does not use global post if it is already filtered in a way other than requested.

[johanee]

First part (to get_post()) looks really weird, not sure what the purpose is. Won't the "isset($GLOBALSpost?->ID)" branch result in an infinite recursion?

[ryan]

(In [12062]) Improve sanitize_post() performance. Perform raw filtering only once. Add filter check to eliminate double filtering. Props johanee. fixes #10972 see #10801