Error : Cannot modify header information –

I am facing error “Cannot modify header information “

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I am non-technical , nothing know about coding.

Please guide how solve this problem.

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In errorlog.php (cpannel ) I found following;

Cannot modify header information – headers already sent by (output started at /home/billinfo/public_html/wp-includes/embed.php:792)

787         if ( ! headers_sent() ) {

788                         $server->send_header( ‘Content-Type’, ‘text/xml; charset=’ . get_option( ‘blog_charset’ ) );

790         }

791

792         echo $result;

793

794         return true;

=======

Resulted error

in /home/billinfo/public_html/wp-includes/rest-api.php on line 731

723 function rest_send_cors_headers( $value ) {

724??$origin = get_http_origin();

??????????????? if ( $origin ) {
??????????????????????????????? // Requests from file:// and data: URLs send "Origin: null".

????? if ( 'null' !== $origin ) {????????????????????? $origin = sanitize_url( $origin );?????????????????????????????? }

731??header( 'Access-Control-Allow-Origin: ' . $origin );

732??header( 'Access-Control-Allow-Methods: OPTIONS, GET, POST, PUT, PATCH, DELETE' );

733? header( 'Access-Control-Allow-Credentials: true' );

734??header( 'Vary: Origin', false ); ??????????????? } elseif ( ! headers_sent() && 'GET' === $_SERVER['REQUEST_METHOD'] && ! is_user_logged_in() )

 

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