HttpOnly for Server-side Cookies

[Kevinlearynet]

When running WordPress at government regulated and/or security focused organizations security audits routinely flag issues with PHP creating cookies without the HttpOnly argument set to true.

While this can't be done for cookies that are used by JavaScript, it can be safely enabled for server-side only cookies set within wp-login.php:

• TEST_COOKIE
• wp-postpass_{HASH}

I've tested this on the latest WordPress trunk with a server stack that mirrors Kinsta and WPEngine. This stack passes 100% of Site Health checks, and is running on the following:

Darwin 23.6.0 x86_64
nginx/1.25.5
PHP 8.3.7 (support 64bit values)
Zend OPcache v8.3.7
mysql 8.3.0 / mysqlnd 8.3.7
8.7.1 (SecureTransport) OpenSSL/3.3.0

Originally reported by earthman100

Trac ticket: https://core.trac.wordpress.org/ticket/61322

[github-actions]

Hi @Kevinlearynet! 👋

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[github-actions]

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Props kevinlearynet, johnbillion.

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[github-actions]

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[Kevinlearynet]

Are these test actions reliable?

I re-triggered tests with a --no-commit that changed nothing, and I see completely different results?

1. First test run shows 10 errors with specific PHP versions and MySQL/MariaDB combinations
2. First test run shows 7 entirely different errors related to SCRIPT_DEBUG and applications-passwords.test.js

[johnbillion]

Not sure what was up with those performance tests but I merged the trunk branch into this and they seem pretty stable again.

[johnbillion]

I support setting the test cookie and wp_lang cookie to HttpOnly, but I don't think it's safe to do it for the post password cookie. There's too high an opportunity for it to break either JavaScript that reads the value of the cookie, or Ajax handlers in PHP that read the value of the cookie, both of which would no longer be able to do so.

Let's revert this change but keep the other changes.

[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 59671
GitHub commit: 2adec31

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.

[Kevinlearynet]

@johnbillion

Thanks! Glad the unit tests work on trunk w/o issues