WooPayments Incompatible after version 7.4.0

Please check this GitHub ticket to understand the problem: https://github.com/Automattic/woocommerce-payments/issues/8500

Response:

With the aforementioned Brevo plugin specifically, we are finding that it is adding the following to the settings?_locale=user network response:

<input type="hidden" class="ws_opt_in_nonce" name="ws_opt_in_nonce" value="[nonce]">

Passing this value through the network response prevents the WooPayments pages from loading. You can test this without the Brevo integration installed by overriding the content of the settings?_local=user request…

…and removing the <input> tag…

From there, use CMD + S or CTRL + S to save your override changes, then refresh the page. It should load as expected.

Alternatively, if the page is loading for you (e.g., you reverted to version 7.3.0 or the Brevo integration is deactivated) you can reproduce this issue by adding any HTML to the request. While <input> is added by the Brevo integration, other HTML tags like <p> and <em> will produce the same issues.

What we suspect is happening here is that the 6a22e18 commit introduced the wocommerce_checkout_fields filter, which is triggering an opt-in via the Brevo integration.

This is not an issue that can or will address in WooPayments. According to the WordPress developer Handbook:

[…] filters are meant to work in an isolated manner, and should never have side effects such as affecting global variables and output.

While we could prevent that from our side by using output buffering before calling the filters, this could lead to other conflicts. As a result, it is best for the developers of the Brevo integration (or similar plugins that may be causing this issue) to resolve this.

Many thanks for all of the reports, as they allowed us to isolate the cause! Given that this is a conflict with a third-party integration and that we will be unable to resolve it within WooPayments specifically, I will close this issue.

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