_json_wp_die_handler doesn't handle JSONP request

[spacedmonkey]

Originally raised in #45933 , but the new wp_die handler _json_wp_die_handler doesn't support JSONP requests and returns invalid response. The rest api support returning JSONP responses, this handler should too.

[spacedmonkey]

Related: #45933

[pento]

Setting Milestone to 5.1 for review.

[spacedmonkey]

Added another handler for jsonp. Also add another function wp_is_jsonp_request.

Can you review please @flixos90

[TimothyBlynJacobs]

The REST API also sends an X-Content-Type-Options: nosniff header which is accompanied by this doc:

/*
 * Mitigate possible JSONP Flash attacks.
 *
 * https://miki.it/blog/2014/7/8/abusing-jsonp-with-rosetta-flash/
 */

Seems this should also be sent in this handler.

[spacedmonkey]

After feedback from @timothyblynjacobs I have added the following lines to add extra headers.

header( 'X-Content-Type-Options: nosniff' );
header( 'X-Robots-Tag: noindex' );

One fixes cors issue and one is SEO related.

[flixos90]

This ticket is based on the old fatal error recovery mode implementation and will be covered as part of #46130.

[spacedmonkey]

Re-opened as still valid and should be another ticket an #46130.

[SergeyBiryukov]

Restoring the milestone.

[SergeyBiryukov]

Moving to 5.2, per the ​latest #core-php chat.

[SergeyBiryukov]

In 45015:

Bootstrap/Load: Add support for JSONP requests to wp_die().

In addition to AJAX, XML-RPC, and JSON requests, wp_die() now handles JSONP requests correctly, returning information in the expected content type.

Props spacedmonkey, TimothyBlynJacobs.
Fixes #46025. See #44458.

[SergeyBiryukov]

In 45017:

Docs: Improve documentation for wp_die() handlers after [45015] and [45016].

See #46543, #46025, #46026.