Prerequisites

• I have carried out troubleshooting steps and I believe I have found a bug.
• I have searched for similar bugs in both open and closed issues and cannot find a duplicate.

Describe the bug

When WooCommerce Square is enabled while using WooCommerce 6.1, the following errors appear on the admin dashboard:

Deprecated: is_ajax is deprecated since version 6.1.0! Use wp_doing_ajax instead. in /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php on line 5211

Deprecated: is_ajax is deprecated since version 6.1.0! Use wp_doing_ajax instead. in /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php on line 5211

Warning: Cannot modify header information - headers already sent by (output started at /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php:5211) in /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php on line 6712

Warning: Cannot modify header information - headers already sent by (output started at /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php:5211) in /srv/users/user029810a9/apps/user029810a9/public/wp-admin/includes/misc.php on line 1310

Warning: Cannot modify header information - headers already sent by (output started at /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php:5211) in /srv/users/user029810a9/apps/user029810a9/public/wp-admin/admin-header.php on line 9

Warning: Cannot modify header information - headers already sent by (output started at /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php:5211) in /srv/users/user029810a9/apps/user029810a9/public/wp-includes/option.php on line 1097

Warning: Cannot modify header information - headers already sent by (output started at /srv/users/user029810a9/apps/user029810a9/public/wp-includes/functions.php:5211) in /srv/users/user029810a9/apps/user029810a9/public/wp-includes/option.php on line 1098

Downgrading to 6.0 resolves the issue. It seems to be related to the is_ajax deprecation that's been discussed in p6q7sZ-9NO-p2

Expected behavior

There should not be any errors.

Actual behavior

There are errors.

Steps to reproduce

1. Install and activate WooCommerce 6.1.
2. Install and activate Square.
3. Behold the errors.
4. Downgrade to WooCommerce 6.0.
5. The errors disappear.

WordPress Environment

`

WordPress Environment

WordPress address (URL): https://increased-armadillo.jurassic.ninja
Site address (URL): https://increased-armadillo.jurassic.ninja
WC Version: 6.1.0
REST API Version: ✔ 6.1.0
WC Blocks Version: ✔ 6.5.1
Action Scheduler Version: ✔ 3.4.0
WC Admin Version: ✔ 3.0.3
Log Directory Writable: ✔
WP Version: 5.8.3
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: ✔
WP Cron: ✔
Language: en_US
External object cache: –

Server Environment

Server Info: Apache/2.4.52 (Unix) OpenSSL/1.0.2g
PHP Version: 7.4.27
PHP Post Max Size: 1 GB
PHP Time Limit: 300
PHP Max Input Vars: 5000
cURL Version: 7.47.0
OpenSSL/1.0.2g

SUHOSIN Installed: –
MySQL Version: 5.7.33-0ubuntu0.16.04.1-log
Max Upload Size: 512 MB
Default Timezone is UTC: ✔
fsockopen/cURL: ✔
SoapClient: ✔
DOMDocument: ✔
GZip: ✔
Multibyte String: ✔
Remote Post: ✔
Remote Get: ✔

Database

WC Database Version: 6.1.0
WC Database Prefix: wp_
Total Database Size: 4.79MB
Database Data Size: 3.39MB
Database Index Size: 1.40MB
wp_woocommerce_sessions: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_api_keys: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_attribute_taxonomies: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_downloadable_product_permissions: Data: 0.02MB + Index: 0.06MB + Engine InnoDB
wp_woocommerce_order_items: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_order_itemmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_tax_rates: Data: 0.02MB + Index: 0.06MB + Engine InnoDB
wp_woocommerce_tax_rate_locations: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_shipping_zones: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_woocommerce_shipping_zone_locations: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_shipping_zone_methods: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_woocommerce_payment_tokens: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_payment_tokenmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_log: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_actionscheduler_actions: Data: 0.02MB + Index: 0.11MB + Engine InnoDB
wp_actionscheduler_claims: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_actionscheduler_groups: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_actionscheduler_logs: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_commentmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_comments: Data: 0.02MB + Index: 0.09MB + Engine InnoDB
wp_links: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_options: Data: 2.48MB + Index: 0.03MB + Engine InnoDB
wp_postmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_posts: Data: 0.02MB + Index: 0.06MB + Engine InnoDB
wp_termmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_terms: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_term_relationships: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_term_taxonomy: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_usermeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_users: Data: 0.02MB + Index: 0.05MB + Engine InnoDB
wp_wc_admin_notes: Data: 0.05MB + Index: 0.00MB + Engine InnoDB
wp_wc_admin_note_actions: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_wc_category_lookup: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_wc_customer_lookup: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_download_log: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_order_coupon_lookup: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_order_product_lookup: Data: 0.02MB + Index: 0.06MB + Engine InnoDB
wp_wc_order_stats: Data: 0.02MB + Index: 0.05MB + Engine InnoDB
wp_wc_order_tax_lookup: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_product_meta_lookup: Data: 0.02MB + Index: 0.09MB + Engine InnoDB
wp_wc_rate_limits: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_wc_reserved_stock: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_wc_tax_rate_classes: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_wc_webhooks: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_square_customers: Data: 0.02MB + Index: 0.00MB + Engine InnoDB

Post Type Counts

attachment: 1
page: 7
post: 2

Security

Secure connection (HTTPS): ✔
Hide errors from visitors: ❌Error messages should not be shown to visitors.

Active Plugins (4)

Companion Plugin: by Osk – 1.21
Jetpack: by Automattic – 10.5
WooCommerce Square: by WooCommerce – 2.7.0
WooCommerce: by Automattic – 6.1.0

Inactive Plugins (2)

Akismet Anti-Spam: by Automattic – 4.2.1
Hello Dolly: by Matt Mullenweg – 1.7.2

Settings

API Enabled: –
Force SSL: –
Currency: USD ($)
Currency Position: left
Thousand Separator: ,
Decimal Separator: .
Number of Decimals: 2
Taxonomies: Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

Taxonomies: Product Visibility: exclude-from-catalog (exclude-from-catalog)
exclude-from-search (exclude-from-search)
featured (featured)
outofstock (outofstock)
rated-1 (rated-1)
rated-2 (rated-2)
rated-3 (rated-3)
rated-4 (rated-4)
rated-5 (rated-5)

Connected to WooCommerce.com: –

WC Pages

Shop base: #6 - /shop/
Cart: #7 - /cart/
Checkout: #8 - /checkout/
My account: #9 - /my-account/
Terms and conditions: ❌ Page not set

Theme

Name: Twenty Twenty-One
Version: 1.4
Author URL: https://wordpress.org/
Child Theme: ❌ – If you are modifying WooCommerce on a parent theme that you did not build personally we recommend using a child theme. See: How to create a child theme
WooCommerce Support: ✔

Templates

Overrides: –

Action Scheduler

Complete: 1
Oldest: 2022-01-13 21:39:34 +0000
Newest: 2022-01-13 21:39:34 +0000

Status report information

Generated at: 2022-01-13 22:27:48 +00:00
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Isolating the problem

• I have deactivated other plugins and confirmed this bug occurs when only WooCommerce plugin is active.
• This bug happens with a default WordPress theme active, or Storefront.
• I can reproduce this bug consistently using the steps above.