shortcode_atts_{$shortcode} – Hook | Developer.WordPress.org
Filters shortcode attributes.
Description
If the third parameter of the shortcode_atts() function is present then this filter is available.
The third parameter, $shortcode, is the name of the shortcode.
Parameters
$outarrayThe output array of shortcode attributes.
$pairsarrayThe supported attributes and their defaults.
$attsarrayThe user defined shortcode attributes.
$shortcodestringThe shortcode name.
Source
$out = apply_filters( "shortcode_atts_{$shortcode}", $out, $pairs, $atts, $shortcode );