site-kit-wp: Ad Blocker detected despite no such ad blocker active

Bug Description

As reported in #1491 one user is unable to view their AdSense dashboards within Site Kit, with an Ad Blocker notice appearing. This notice appears despite checking while in troubleshooting mode using the Health Check & Troubleshooting plugin - from a Chrome browser incognito window

Ad AdSense level the below is reported:

Your site isn’t ready to show ads
We’ve found some policy violations on your site which means your site isn’t ready to show ads yet.

Screenshots

There are some Ad Block code references when checking the users source code

Console errors that appear below

CORS policy notices

Additional context

• Site is not approved at AdSense level yet
• User does have AdSense traffic (via YouTube)
• User is unable to open WP support topic

Insights & Troubleshooting Checks performed

• Health Check & Troubleshooting plugin check
• Incognito mode
• Checked users Site Health info, no identified causes
• Confirmed no modification of Site Kit placed snippet
• Uninstalled and reinstalled plugin
• User confirmed no “Critical errors” in their Site Health status
• Attempted setup/viewing dashboards from another device
• Temporary disabled WAF rules at host level - including ModSecurity
• Checked site setup and dashboard from another WordPress site on the same hosting platform
• Disconnected Site Kit
• Disconnected impacted service and connected once more
• Reviewed error logs
• Reviewed XHR requests

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Implementation Brief

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Changelog entry