Errors after update to 5.3.1

[caraya]

I am getting the following errors when previewing a post after upgrade to 5.3.1

public-api.wordpress.com/wp-admin/rest-proxy/?v=2.0:6 WebSocket connection to 'wss://public-api.wordpress.com/pinghub/wpcom/me/newest-note-data' failed: Error during WebSocket handshake: Unexpected response code: 403

==/?p=789855&preview_id=789855&preview_nonce=8860e6b287&post_format=standard&_thumbnail_id=-1&preview=true:1 Failed to set referrer policy: The value 'is not one of 'no-referrer', 'no-referrer-when-downgrade',
'origin', 'origin-when-cross-origin', 'same-origin', 'strict-origin', 'strict-origin-when-cross-origin', or 'unsafe-url'. The referrer policy has been left unchanged.
}}}

Normally I wouldn't have noticed but it keeps reloading my syntax highlighter plugin and changing the way that code looks in the post. The same errors happen in Firefox Nightly, Chrome Canary (80) and Crome Stable (79)

[audrasjb]

Hi @caraya thank you for this ticket and welcome to WordPress Trac!

Looks like an issue with your plugin. Could you please mention its name?

(adding close keyword as it seems to be plugin related)

[SergeyBiryukov]

To clarify a bit, WordPress core does not have any references to public-api.wordpress.com/wp-admin/rest-proxy/, so this does seem like a plugin issue.

Does it still happen with all plugins disabled and a default theme (Twenty Twenty) activated?

[audrasjb]

Closing this ticket as invalid (which is Trac resolution keyword used for tickets that are not related to WP Core) after waiting for reporter feedback, as it doesn't looks to be related to WordPress Core.

Feel free to reopen the ticket if you have further information about the context of the issue.