<style> tag stripped from start of source in TinyMCE v6

Questions
1

Hi there,

We have a requirement to let our website editors add custom styles in TinyMCE source code.

This worked fine in v10, but after upgrading to v13 (currently on v13.5.3), <style> tags can only be added at the end of the generated source code in TinyMCE v6 editors.

If website editors add <style> tags at the beginning of the source code, it gets stripped by Umbraco upon submitting the changes.

This is our custom config:

"CustomConfig": {
          "entity_encoding": "raw",
          "font_size_formats": "8px 9px 10px 11px 12px 14px 15px 16px 18px 20px 21px 22px 24px 26px 28px 36px 48px 72px",
          "content_style": "body {font-size: 11px;}",
          "custom_elements": "style",
        }

Is there something we are missing?

Many thanks in advance for your help!