Preconditions (*)

1. Any Magento version that includes a suggested Varnish VCL config.
2. Using Varnish along with a VCL that is included with Magento.
3. Usage of Klaviyo's marketing email services/modules.

Steps to reproduce (*)

1. Use a VCL that is included with Magento.
2. Send a marketing email via Klaviyo.
3. Watch varnishlog.
4. Visit the site using a link that is included in a Klaviyo-generated email.
5. Visit the site using a similar link that does not include the _kx query parameter.
6. Compare the results shown by varnishlog.

Expected result (*)

1. The _kx parameter should be stripped, ensuring that visitors using links with the _kx parameter are served the cached version of the requested page.

Actual result (*)

1. Varnish does not strip the parameter, and since the value is unique per visitor, those requests will not match any hashes in Varnish's cache.
2. This also results in additional PHP load due to the request needing to be processed by Magento.

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Please provide Severity assessment for the Issue as Reporter. This information will help during Confirmation and Issue triage processes.

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.