Title: error: “cannot modify header…” since update
Last modified: March 27, 2021

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# error: “cannot modify header…” since update

 *  Resolved [horiamar](https://wordpress.org/support/users/horiamar/)
 * (@horiamar)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/)
 * Hello there, I would need help with the following error that occurs since update
   of the plugin to ver 2.5.6! What could be the reason of this error? Thank you
   in advance!
 * Warning: Cannot modify header information – headers already sent by (output started
   at /home/customer/www/mybrandies.com/public_html/wp-content/plugins/woocommerce-
   stock-manager/admin/class-stock-manager-admin.php:493) in /home/customer/www/
   mybrandies.com/public_html/wp-includes/functions.php on line 6362
 * here are the code parts this error refers to:
    line 493 in **class-stock-manager-
   admin.php**:
 *     ```
       <style type="text/css">
       				#wsm_promo_msg {
       					display: block !important;
       					background-color: #f2f6fc;
       					color: #fff;
       					border-left-color: #5850ec;
       				}
       ```
   
 * line 6362 in **functions.php**:
 *     ```
       if ( ! did_action( 'wp_loaded' ) ) {
       		/**
       		 * Filters the list of protocols allowed in HTML attributes.
       		 *
       		 * @since 3.0.0
       		 *
       		 * @param string[] $protocols Array of allowed protocols e.g. 'http', 'ftp', 'tel', and more.
       		 */
       		$protocols = array_unique( (array) apply_filters( 'kses_allowed_protocols', $protocols ) );
       	}
       ```
   
    -  This topic was modified 5 years, 2 months ago by [horiamar](https://wordpress.org/support/users/horiamar/).
 * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Ferror-cannot-modify-header-since-update%2F%3Foutput_format%3Dmd&locale=en_US)
   to see the link]_

Viewing 9 replies - 1 through 9 (of 9 total)

 *  Thread Starter [horiamar](https://wordpress.org/support/users/horiamar/)
 * (@horiamar)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14246967)
 * Adding to my bug description above the following:
 * I entered “Troubleshooting Mode” and tested if the WooCommerce Stock Manager 
   still does the same error: with all themese deactivated (only **theme “2021” **
   active!) and all plugins deactivated, except **WooCommerce** and **Woocommerce
   Stock Manager**, the website still sends the same error message I cited here 
   above, while in “admin dashboard” mode:
 * >  Warning: Cannot modify header information – headers already sent by (output
   > started at /home/customer/www/mybrandies.com/public_html/wp-content/plugins/
   > woocommerce-stock-manager/admin/class-stock-manager-admin.php:493) in /home/
   > customer/www/mybrandies.com/public_html/wp-includes/functions.php on line 6362
    -  This reply was modified 5 years, 2 months ago by [horiamar](https://wordpress.org/support/users/horiamar/).
 *  Thread Starter [horiamar](https://wordpress.org/support/users/horiamar/)
 * (@horiamar)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14247130)
 * I uninstalled the version 2.5.6 and installed instead the version 2.5.5. Result:
   no more error (as described above). So it is definitely a bug that was introduced
   in the last update of this plugin.
 *  [the0bone](https://wordpress.org/support/users/the0bone/)
 * (@the0bone)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14262905)
 * Have the same issue since the new version.
 *  [dkintheuk](https://wordpress.org/support/users/dkintheuk/)
 * (@dkintheuk)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14265913)
 * Same problem here… three different lines showing errors but all errors are “headers
   already sent”.
 *  Thread Starter [horiamar](https://wordpress.org/support/users/horiamar/)
 * (@horiamar)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14267229)
 * It is not quite encouraging to use this plugin (or pay for an upgrade), if there
   is no reply whatsoever from the side of the developer for five days…
 *  Plugin Author [storeapps](https://wordpress.org/support/users/storeapps/)
 * (@storeapps)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14267248)
 * Hi there,
 * We are looking into this and will update soon.
 *  Plugin Author [storeapps](https://wordpress.org/support/users/storeapps/)
 * (@storeapps)
 * [5 years, 2 months ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14271445)
 * Hi there,
 * We have released a new version 2.5.7 which should fix this issue.
 * Kindly update to the latest version and then have a check with the functionality.
 * Let us know if it works correctly after that.
 *  Thread Starter [horiamar](https://wordpress.org/support/users/horiamar/)
 * (@horiamar)
 * [5 years, 1 month ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14293031)
 * [@storeapps](https://wordpress.org/support/users/storeapps/)
    thank you for your
   reply and update! that’s great news! I will test the new version 2.5.7!
 *  Plugin Author [storeapps](https://wordpress.org/support/users/storeapps/)
 * (@storeapps)
 * [5 years ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14501144)
 * Hi horiamar,
 * You are welcome.
 * If you are liking the plugin, please consider leaving a 5-star review from [here](https://wordpress.org/support/plugin/woocommerce-stock-manager/reviews/#new-post).

Viewing 9 replies - 1 through 9 (of 9 total)

The topic ‘error: “cannot modify header…” since update’ is closed to new replies.

 * ![](https://ps.w.org/woocommerce-stock-manager/assets/icon-256x256.png?rev=2354654)
 * [Stock Manager for WooCommerce](https://wordpress.org/plugins/woocommerce-stock-manager/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/woocommerce-stock-manager/#faq)
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 * [Active Topics](https://wordpress.org/support/plugin/woocommerce-stock-manager/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/woocommerce-stock-manager/unresolved/)
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## Tags

 * [Cannot modify header information](https://wordpress.org/support/topic-tag/cannot-modify-header-information/)

 * 9 replies
 * 4 participants
 * Last reply from: [storeapps](https://wordpress.org/support/users/storeapps/)
 * Last activity: [5 years ago](https://wordpress.org/support/topic/error-cannot-modify-header-since-update/#post-14501144)
 * Status: resolved