MIME Type Validation

Validate files by their actual MIME type detected from magic bytes, not just the file extension. Catch renamed executables and scripts.

What you should see: the file's real content type is checked against .jpg/.png/.gif, not just its extension. Rename a .txt to .jpg and it is still caught.

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MIME type checking is performed automatically. Try renaming a .exe to .jpg and uploading it - it will be rejected.

<!-- MIME type validation is automatic when extensions are set -->
<core-upload asp-upload-url="/api/upload/upload"
 asp-extensions=".jpg,.png,.gif"
 asp-multiple="true"
 asp-progress="true">
</core-upload>