WordPress at a glance
filter is not described

http_request_reject_unsafe_urls filter-hook . WP 3.6.0

Filters whether to pass URLs through wp_http_validate_url() in an HTTP request.

Usage

add_filter( 'http_request_reject_unsafe_urls', 'filter_function_name_4373' );
function filter_function_name_4373( $pass_url ){
	// filter...

	return $pass_url;
}
$pass_url(true/false)
Whether to pass URLs through wp_http_validate_url().
Default: false

Where the hook is called

WP_Http::request()
wp-includes/class-http.php 192
'reject_unsafe_urls' => apply_filters( 'http_request_reject_unsafe_urls', false ),

Where the hook is used (in WP core)

Does not used.