Magento Security Patch October 2026: Install and Verify the BlockStrap Fix Before Peak

October 24, 2026 · 11 min read

If you run Magento Open Source, Adobe Commerce or Mage-OS, install the October 2026 security patch (Adobe bulletin APSB26-153) this week and confirm the code change is present on the server. The patch fixes CVE-2026-103849, which the security firm Sansec named "BlockStrap" and scored CVSS 10.0: an unauthenticated attacker could run PHP code on your store server. As of October 24, 2026, Sansec reports no exploitation in the wild, but it reproduced four working attack routes within 24 hours of the patch release.

The October patch does not replace the September emergency hotfix VULN-39341 for StyleSmuggler (CVE-2026-75650). You need both. A deploy log that says "success" does not prove either is applied, so check the files directly with the commands below.

At a glance

• Affected, per Sansec: Adobe Commerce and Magento Open Source up to 2.4.9, Adobe Commerce B2B up to 1.5.3, Mage-OS up to 3.5.0.
• Fixed in Magento Open Source 2.4.7-p10, 2.4.8-p5 and 2.4.9 (public patches), 2.4.4-p18, 2.4.5-p17 and 2.4.6-p15 (Adobe Commerce licence required), and Mage-OS 3.6.0.
• Adobe rated the bulletin priority 2 (a 30-day window). Sansec argues the risk is closer to the September zero-day, which went from hotfix to mass exploitation in three days.
• Keep or install VULN-39341 as well. Adobe's registry does not list it as a prerequisite for the October patch.
• Verify with grep, not with the deploy result. Patch tools can skip hunks without failing.
• After patching, watch the storefront for injected scripts and unexpected redirects. Patching does not clean a store that was already compromised.

Why the October patch matters now

Two Magento remote code execution bugs landed six weeks apart, both in the email template engine.

On September 4, 2026, attackers began exploiting StyleSmuggler (CVE-2026-75650, CVSS 10.0) before any fix existed. Adobe published hotfix VULN-39341 on September 7 under bulletin APSB26-146. Sansec documented what attackers installed on compromised stores: a Rust backdoor disguised as system processes, a PHP web shell in the product image cache, and a base64 card skimmer stored in the core_config_data table under design/head/includes, which loads on every store view.

On October 13, Adobe published APSB26-153. According to Sansec's analysis of October 15, BlockStrap exposes a gap left by the StyleSmuggler fix: a child email template is signed and then processed again at the root level, which executes an injected {{block}} directive. On October 14, Adobe replaced the 2.4.8-p5 patch file and published a separate isolated fix for CVE-2026-91013, a second issue on that release line.

Sansec told BleepingComputer that "anyone with an AI agent can reverse-engineer the patch into working exploits in a relatively short time." Whether or not that happens before your next release window, the calendar argues for acting now. Most stores freeze code in November, and a 30-day patch window that starts on October 13 ends inside Black Friday week.

Store databases are also under separate attack. On October 24, Sansec published research on a loader campaign that has hit 953 Magento stores since July 2025, injecting JavaScript into the cms_block table. Sansec does not link that campaign to BlockStrap, but it shows where to look once you have patched.

Step-by-step: patch and verify today

1. Record what you run. In the Magento root, run composer show magento/product-community-edition (or magento/product-enterprise-edition, or mage-os/product-community-edition) and note the exact version and patch level.
2. Take a backup you have restored before. If you have never restored a database dump and code snapshot, you do not yet know whether you can roll back. Our guide on testing a backup restore covers a safe way to prove it.
3. Check the September hotfix first: vendor/bin/magento-patches -n status | grep "39341\|Status". If VULN-39341 is not applied, install it from repo.magento.com before the October patch.
4. Pick your October route. If you are on a supported line, upgrade to 2.4.7-p10, 2.4.8-p5 or 2.4.9. Adobe Commerce customers on 2.4.4 to 2.4.6 can use the licensed releases listed above. Mage-OS stores upgrade the mage-os/product-community-edition metapackage to 3.6.0. If you are below 2.4.7 on Open Source, Sansec's advice is to upgrade to 2.4.7-p10 or later. Third-party backports exist (Happy Horizon published patches for 2.4.4-p18 through 2.4.9), but Sansec states it gives no warranty for them.
5. On 2.4.8-p5, apply the isolated patch 248p5-2026-10-002-CE for CVE-2026-91013.
6. Deploy to staging, run your checkout test, then deploy to production during a low-traffic hour.
7. Verify on production, not just staging, using the checks in the test plan below.
8. Clear caches and test the purchase path again: product page, cart, checkout, payment, order confirmation email. The patch touches the email template engine, so send yourself a real order confirmation and a password reset email.
9. Log the deploy time. If an issue shows up later, you want to see it next to the patch on one timeline. The post-deployment checklist lists the checks to run after any release.

If you cannot patch within hours, Sansec says its Shield product blocks BlockStrap at the HTTP layer. For the September flaw, Cloudflare and Imperva shipped WAF rules on September 10. A WAF rule buys time. It does not replace the patch.

Who checks what

Risk	Owner	Check	Frequency
October fix missing on a server	Developer or agency	grep -c resolveDeferredDirectives on Filter/Template.php returns 1 or more	After every deploy until peak ends
September hotfix missing	Developer or agency	magento-patches -n status shows VULN-39341 applied	After every deploy
2.4.8-p5 isolated fix missing	Developer	grep -c QUOTED_LOCAL_PART_PATTERN on EmailAddress.php returns 1 or more	Once after patching
Injected script in head or CMS blocks	Developer, store manager reviews	Query core_config_data and cms_block for unexpected script tags	Weekly through January
Unknown admin accounts	Store owner	Review admin_user list against staff list	Weekly
Storefront redirects shoppers elsewhere	Agency or monitoring	External check from several regions and a mobile user agent	Continuous
Order emails broken by template changes	Store manager	Place a test order and confirm the email arrives	After patching, then daily in peak

Copyable test plan

Run these from the Magento root on each production server. Paste the output into your change ticket.

# 1. Version and patch level
composer show magento/product-community-edition 2>/dev/null | grep -E '^versions'

# 2. October 2026 fix (APSB26-153 / BlockStrap). 0 = fix missing
grep -c resolveDeferredDirectives vendor/magento/framework/Filter/Template.php
# Mage-OS: grep -c resolveDeferredDirectives vendor/mage-os/framework/Filter/Template.php

# 3. September 2026 hotfix (VULN-39341 / StyleSmuggler)
vendor/bin/magento-patches -n status | grep "39341\|Status"

# 4. 2.4.8-p5 only: CVE-2026-91013 fix. 0 = apply 248p5-2026-10-002-CE
grep -c QUOTED_LOCAL_PART_PATTERN vendor/magento/framework/Validator/EmailAddress.php

# 5. Post-patch hygiene: scripts in global head and CMS content
mysql -e "SELECT path, scope_id FROM core_config_data WHERE path LIKE 'design/head/%' AND value LIKE '%<script%';" <db>
mysql -e "SELECT block_id, identifier, update_time FROM cms_block WHERE content LIKE '%localStorage.getItem%' OR content LIKE '%fpCode%' ORDER BY update_time DESC;" <db>
mysql -e "SELECT username, email, created FROM admin_user ORDER BY created DESC LIMIT 20;" <db>

Sign-off criteria:

• [ ] Check 2 returns 1 or more on every production node
• [ ] Check 3 shows VULN-39341 as applied
• [ ] Check 4 returns 1 or more (2.4.8-p5 only)
• [ ] Every script in design/head is one your team added on purpose
• [ ] No unexplained cms_block changes since September 1
• [ ] Every admin user matches a current person
• [ ] Test order placed, paid, and confirmation email received

After the October patch you may see an empty file in the Magento root named 976bc24c08055e67a58cf491401c8b2f3d48ff55b8092f1ede196bac4756a228. Sansec identifies it as a known side effect (GitHub issue magento/magento2#41535), not an attack. You can delete it or add it to .gitignore.

Worked scenario (illustrative)

A freelancer maintains three Magento stores for different clients. Store A runs 2.4.8-p4, Store B runs 2.4.7-p9, and Store C runs 2.4.5 on Open Source with no recent upgrades.

On Monday the freelancer runs the test plan on all three. Store A already has VULN-39341 from September. Store B does not, because the September hotfix went onto staging and nobody promoted it. Store C has neither, and Adobe publishes no public October patch for 2.4.5 Open Source.

Store A moves to 2.4.8-p5 with the isolated patch the same evening. Store B gets VULN-39341 and then 2.4.7-p10 on Tuesday. For Store C, the freelancer puts a WAF rule in front of the site, tells the client in writing that the store needs an upgrade to 2.4.7-p10 before peak, and books the work for the following week. While running check 5 on Store C, the freelancer finds a design/head/includes value with a base64 script nobody on the team added. Store C now gets incident treatment: remove the script, rotate the encryption key and every credential it protected, and review the server for backdoors before anyone calls the upgrade done.

The numbers and stores here are invented to show the order of work.

Common mistakes

• Treating the October patch as cumulative. It does not include VULN-39341, and Sansec says you need both.
• Trusting the deploy log. Run the grep checks on each production node, including any node added by autoscaling.
• Patching staging only. Store B in the scenario is a common pattern.
• Waiting for Adobe's 30-day priority window when it ends inside your freeze. The code freeze article explains how to define a security exception before peak starts.
• Assuming a patched store is clean. Sansec warns that patching does not remove an attacker who got in earlier, and that stores hit by StyleSmuggler were exposed for three days before any fix existed. Rotating the encryption key alone does not invalidate credentials an attacker already read.
• Reading the absence of alerts as proof. A skimmer or loader can serve normal pages to scanners and malicious code only to real shoppers. See why a site can return 200 and still be hacked.

Limitations: this article covers the October 2026 bulletin and the September hotfix as reported by Sansec and BleepingComputer up to October 24, 2026. It does not replace Adobe's bulletin, and the commands assume a standard Composer install. If you find signs of compromise, bring in an incident response specialist and contact your payment provider.

FAQ

Is my store vulnerable if I already installed the September hotfix?

Yes, if you have not installed the October patch. Sansec states that the StyleSmuggler hotfix alone does not stop BlockStrap. Run check 2 to confirm.

Does Adobe Commerce Cloud apply this patch for me?

Do not assume it does. Run the version and grep checks on your Cloud environment the same way, and confirm with your Adobe account team if the output shows the fix missing.

My store runs Magento 2.3 or 2.4.0 to 2.4.3. What now?

Adobe published nothing for 2.2, 2.3 or 2.4.0 to 2.4.3 for the September flaw, and the October public fixes start at 2.4.7-p10 for Open Source. Put a WAF rule in front of the store now and plan an upgrade. Third-party backports exist, and Sansec says it has not reviewed them.

Sources

• Sansec, "BlockStrap: Magento and Adobe Commerce RCE (CVE-2026-103849)", October 15, 2026: https://sansec.io/research/blockstrap-magento-rce
• Sansec, "StyleSmuggler: Magento and Adobe Commerce 0-day RCE (CVE-2026-75650) under active attack", September 2026: https://sansec.io/research/stylesmuggler-0day
• Sansec, "Magento CMS block loader hits 953 stores", October 24, 2026: https://sansec.io/research/magento-cms-block-loader-deepveindrilling
• BleepingComputer, "Critical BlockStrap flaw lets hackers run code on Magento servers", October 16, 2026: https://www.bleepingcomputer.com/news/security/critical-blockstrap-flaw-lets-hackers-run-code-on-magento-servers/
• Adobe Experience League, Magento Open Source 2.4.8 security patch release notes: https://experienceleague.adobe.com/en/docs/commerce-operations/release/notes/security-patches/2-4-8-patches

Last reviewed: 2026-10-24

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Pingvera can cover the last row of the table for you. It checks the storefront from several regions and with a mobile user agent, flags unexpected redirects to foreign domains, and puts your patch deploy on the same timeline as any incident that follows. It does not scan your server or install patches; the steps above stay with your developer.

Read next: Black Friday Email Deliverability: 2026 Store Checklist · Black Friday Code Freeze 2026: What to Lock and Still Patch · Website Maintenance Onboarding Checklist · Ecommerce Replatforming Checklist · Run a free site check.