- Comments: Prevent users who can not see a post from seeing comments on it.
- Shortcodes: Restrict media shortcode ajax to certain type.
- REST API: Ensure no-cache headers are sent when methods are overridden.
- Prevent unintended behavior when certain objects are unserialized.
Merges [56834], [56835], [56836], and [56838] to the 4.5 branch.
Props xknown, jorbin, joehoyle, timothyblynjacobs, peterwilsoncc, ehtis, tykoted, antpb, rmccue.
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