Fix the “Sorry, this file type is not permitted for security reasons.” issue on WordPress while uploading an SVG file

fix-svg-upload-error-in-wordpress.php

<?php
/**
	 * A workaround for upload validation which relies on a PHP extension (fileinfo) with inconsistent reporting behaviour.
	 * ref: https://core.trac.wordpress.org/ticket/39550
	 * ref: https://core.trac.wordpress.org/ticket/40175
	 */
	function prefix_filter_fix_wp_check_filetype_and_ext( $data, $file, $filename, $mimes ) {
		if ( ! empty( $data['ext'] ) && ! empty( $data['type'] ) ) {
			return $data;
		}
  
		$registered_file_types = ['svg' => 'image/svg+xml|application/octet-stream|image/x-svg+xml'];// add other non-supported mime types if needed 
		$filetype = wp_check_filetype( $filename, $mimes );

		if ( ! isset( $registered_file_types[ $filetype['ext'] ] ) ) {
			return $data;
		}

		return [
			'ext' => $filetype['ext'],
			'type' => $filetype['type'],
			'proper_filename' => $data['proper_filename'],
		];
	}
	/**
	 * Allow files with .svg extension to be uploaded via
	 * the wordpress media uploader
	 *
	 * 
	 * @param array $mime_types Existing allowed mime types
	 * @return array
	 */
	function prefix_allow_svg( $mime_types ) {

		if ( ! in_array( 'svg', $mime_types ) ) { // Check if it hasn't been enabled already
			// allow SVG file upload
			$mime_types['svg'] = 'image/svg+xml|application/octet-stream|image/x-svg+xml';
		}

		return $mime_types;
	}

add_filter( 'wp_check_filetype_and_ext', 'prefix_filter_fix_wp_check_filetype_and_ext', 10, 4 );
add_filter( 'upload_mimes', 'prefix_allow_svg' );