[Bug]: Herd 1.24.2 + PHP 8.3.29 outputs literal "8"-->" in WordPress HTML

[BartoszMacek]

Platform

macOS

Operating system version

macOS: Tahoe 26.1

System architecture

Apple M3, Apple Silicon

Herd Version

1.24.2 (Build 59)

PHP Version

PHP 8.3.29

Bug description

Environment

• Herd version: 1.24.2 (latest)
• PHP versions tested: 8.2, 8.3.29, 8.5 (bug occurs on all)
• OS: macOS
• CMS: WordPress 6.9 (multiple sites affected)

Issue
Herd 1.24.2 injects a literal string 8"--> multiple times in HTML output between closing tags (</style>, </script>) and subsequent opening tags (<link>, <script>).
Reproduction Steps

Install Herd 1.24.2

1. Create any WordPress site (tested on WP 6.9, 6.8, and older versions)
2. View page source (View → Developer → View Source)
3. Search for 8"-->
4. Observe multiple occurrences of this literal string in the HTML

Expected Behavior
Clean HTML output without any injected strings.

Actual Behavior
Literal 8"--> appears between tags:

</style>
8"--><link rel="stylesheet" href="...">

</script>
8"--><script src="...">

Technical Details

• HEX representation: 38222d2d3e (confirms it's literal UTF-8 text, not encoding corruption)
• Pattern: Always appears after closing </style> or </script> tags
• Frequency: 3-6 occurrences per page load (multiplies when logged into WordPress admin)

Debug Information

Nginx config check:

cat ~/Library/Application\ Support/Herd/config/nginx/nginx.conf | grep gzip
# gzip disabled, still occurs

PHP settings:

herd php -i | grep output_buffering
# output_buffering => 0 => 0

Confirmed Working Version

Herd 1.23: Does NOT have this issue (confirmed on colleague's machine)

Workaround

// wp-content/mu-plugins/fix-herd-bug.php
add_action('init', function() {
    ob_start(function($buffer) {
        return str_replace('8"-->', '', $buffer);
    });
}, 1);

Impact

• Visible in page source
• Breaks HTML validation
• Affects all WordPress sites on Herd 1.24.2
• Does not occur on production servers or other local environments

Additional Context
Issue was initially suspected to be:

• WordPress 6.9 bug (ruled out - occurs on WP 6.8 and older)
• PHP version issue (ruled out - occurs on PHP 8.2, 8.3, 8.5)
• Nginx gzip compression (ruled out - disabled, still occurs)
• Output buffering (ruled out - confirmed disabled)

This appears to be a regression introduced between Herd 1.23 and 1.24.2.

Steps to reproduce

1. Fresh WordPress installation on Herd 1.24.2
2. View page source
3. Search for '8"-->'

Relevant log output

[mpociot]

I am unable to reproduce this on a fresh WordPress installation in Herd. I also don't know why Herd should inject something in style or script tags for WordPress to be honest.
Do you maybe have a custom driver that causes this?

[RemyyB]

Hey! I am having this exact same issue on a macbook with Herd. We use a custom Sage theme. I have switched Macbook a few days ago and only having this issue on the new Macbook (where I freshly installed Herd). I have 1 other colleague with the same issue (also on newer Herd after updating).

Switching PHP version did nothing unfortunately.

Is seems to be a very specific MacOS Edge case. The issue is not present on the Windows version (did not test a reinstall yet). It is also not present on a live environment on Linux.

Is there a way to still download the old version? I cannot find it on the website anymore.

@BartoszMacek did you every find a real solution?

[BartoszMacek]

@RemyyB
Hi, it’s nice to know someone else is struggling with the same bug. I’ve tried many different solutions, but nothing worked for me.
I tried downgrading Herd and switching PHP versions, but none of that helped.

I’ve noticed that on a fresh WordPress installation this issue doesn’t appear, so it seems to be some kind of conflict with a Sage-related package. I also noticed that when you’re logged in, the 8--> string is doubled.

The bug doesn’t occur on live sites, just on local environment.

If it’s annoying, you can temporarily add this to the very beginning of your functions.php file:

ob_start(function($buffer) {
    $buffer = preg_replace('/\/\*#\s*$/', '', $buffer);
    $buffer = str_replace('8"-->', '', $buffer);
    return $buffer;
});

Just don’t forget to comment it out before pushing to production :)

[RemyyB]

@BartoszMacek we found the solution for us, the problem was a bug in the roots/acorn-prettify package, especially 'clean-html5-markup'. It was fixed for us since version 1.0.4.

So not a Herd bug for us, but a specific edge case in a composer package.

[BartoszMacek]

Thanks @RemyyB it's solved my problem too !