Steps to replicate the issue:

• Go to https://excalidraw.com/
• Create diagram with some text
• Export diagram as SVG[1]
• Attempt to upload as file to MediaWiki

[1]

What happens?:
Upload warning "Found unsafe CSS in the style element of uploaded SVG file.", upload fails

What should have happened instead?:
Upload should succeed without warning

Software version
1.43

Excalidraw exports diagrams with fonts embedded as data URLs with font/woff2 MIME type:

<style>
    @font-face { 
        font-family: Excalifont;
        src: url(data:font/woff2;base64,d09....

This approach seems not limited to Excalidraw: https://github.com/Azgaar/Fantasy-Map-Generator/issues/99