Magento Checkout Issues in CSP Restricted Mode: How to Diagnose and Fix Them Safely

Table of Contents

• Why checkout breaks when restricted mode is enforced
• The most common symptom patterns
• Step 1: Identify where the blocked script is coming from
• Step 2: Choose the safest fix
• Step 3: Treat checkout CSP adjustments as a release
• Common pitfalls to avoid
• Quick “CSP error → fix” reference

CSP Error Background

Magento's Content Security Policy (CSP) is enforced in restrict mode on payment pages by default since version 2.4.7. Shortly after upgrading to 2.4.7+, merchants started experiencing console errors in checkout such as “Refused to execute inline script…”. Adobe has documented this behavior in Knowledge Article (KA)-25030, which explains how inline JavaScript introduced through Admin configuration or Google Tag Manager (GTM) can be blocked when CSP restricted mode is active.

This guide builds on that article. It focuses on how to identify the source of blocked scripts, choose a fix that preserves CSP enforcement, and test changes without introducing new checkout failures.

Why checkout breaks when restricted mode is enforced

Under restricted mode, the checkout CSP header excludes unsafe-inline from script-src, and only explicitly allowed inline scripts can run. Catalog pages often continue to function because they aren’t subject to the same enforcement. Checkout is the first place where violations become visible.

The most common symptom patterns

You may see:

• Console errors about CSP blocking inline scripts
• Checkout UI regressions
• Missing fields or steps that rely on JavaScript
• Third-party tools failing only on checkout (tax validation, address lookups, shipping logic, payment widgets)

Adobe’s KA-25030 ties these issues to inline JavaScript added through Admin and to GTM-related script execution problems.

Step 1: Identify where the blocked script is coming from

Use console errors and page source to classify the origin.

Admin-injected scripts

Scripts added through Admin areas such as header or footer injection are a frequent cause of failures under restricted mode.

GTM containers and Custom HTML tags

GTM often emits inline JavaScript or bootstrap code. In restricted mode, these snippets are blocked unless CSP requirements are met. Adobe also documents a specific issue where GTM custom scripts fail to execute because of CSP; see ACSD-60788.

CMS blocks containing scripts

Support widgets, tracking snippets, and review integrations can introduce inline JavaScript or unapproved third-party domains.

Theme or module inline scripts

Legacy checkout customizations and third-party modules may output inline JavaScript that previously worked but no longer meets CSP rules.

Step 2: Choose the safest fix

The goal is not to relax CSP until checkout works. The goal is to keep checkout predictable, auditable, and compliant.

Fix option 1: Move inline logic into a first-party JS module

If the inline code is yours or a vendor snippet that can be modularized, relocate it into a JavaScript file loaded through Magento’s frontend pipeline.

• Reduces CSP exceptions: Fewer special cases to maintain.
• Removes the need for hash or nonce management: Avoids long-term overhead.
• Improves caching and maintainability: Better long-term stability.

Fix option 2: Hash allowlist stable inline scripts

When a module outputs a deterministic inline block, adding its hash to the allowlist is often the cleanest strict-mode solution.

Fix option 3: Allowlist third-party hosts only when necessary

If an external script is being blocked, you can allowlist its domain, but confirm the script belongs on checkout and review directives such as:

• connect-src for beacons or service calls
• frame-src for hosted fields or iframes
• img-src for tracking pixels

Fix option 4: Nonces or GTM-specific adjustments

Nonce-based approaches can help with certain inline patterns but add operational complexity. If you are troubleshooting GTM issues under CSP, Adobe’s patch ACSD-60788 addresses a case where GTM Custom HTML scripts do not execute because of CSP restrictions.

For more information about where you would use each of these options, refer to our Safe Scripting for Magento blog post.

Step 3: Treat checkout CSP adjustments as a release

Checkout is tightly coupled - a CSP change may appear to solve one issue but create another.

With any CSP change, be sure to test:

• Guest and logged-in checkout
• Shipping and tax recalculation
• Address validation tools
• Each payment method, including 3-D Secure flows
• Mobile checkout
• Order success page tags and events

Common pitfalls to avoid

• Don’t reintroduce unsafe-inline:

  Payment-page CSP is designed to exclude unsafe-inline. Reinstating it weakens controls and reintroduces the risks CSP is meant to reduce.

• Don’t allowlist everything shown in the console:

  This leads to policy sprawl and obscures which scripts actually belong on checkout.

• Don’t rely on GTM Custom HTML for checkout logic:

  Even when technically possible, it creates brittle behavior and makes script governance difficult.

Quick "CSP error → fix" reference

• Refused to execute inline script → move logic to a JS module or hash-allowlist
• External script blocked → verify it belongs on checkout; allowlist host if appropriate
• Tool loads but doesn’t function → review connect-src
• Payment iframe or hosted fields not loading → check frame-src
• GTM custom scripts not executing → review Adobe’s patch ACSD-60788