SVG uploads in the WP Customizer not working

[patrickwc]

Describe the bug

For some reason, when using Safe SVG uploading SVGs used to work within the customizer. Now they do not.

After some time testing, I managed to use a filter on Plupload which enabled uploading (plupload_default_settings)

I think this might be because Customizer uses Plupload, whose default config is missing svg from the allowed file extensions. But it worked before, so I am not sure really. In case it helps, this is what fixed it for me:

if (
			isset( $settings['filters']['mime_types'] )
			&& \is_array( $settings['filters']['mime_types'] )
		) {
			foreach ( $settings['filters']['mime_types'] as &$mime_type ) {
				if (
					isset( $mime_type['extensions'] )
					&& \is_string( $mime_type['extensions'] )
					&& \strpos( $mime_type['extensions'], 'svg' ) === false
				) {
					$mime_type['extensions'] .= ',svg,svgz';
				}
			}
		}

Steps to Reproduce

• Add a custom customizer image via the theme customizer API http://codex.wordpress.org/Theme_Customization_API
• via WP_Customize_Image_Control or WP_Customize_Media_Control
• try and add an SVG.
• The same SVG upload works in the media library, but not via the customizer.

Screenshots, screen recording, code snippet

See #279 (comment)

Environment information

all browsers etc

WordPress information

Latest WP. Tried with all plugins disabled apart from Safe SVG too.

Code of Conduct

• I agree to follow this project's Code of Conduct