How to fix missing content security policy on OpenCart

Steps for OpenCart

1. Edit your .htaccess file (Apache) and add: Header always set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self';"
2. For Nginx, add the add_header directive in your OpenCart server block.
3. Alternatively, modify system/startup.php or a custom controller to call header() before any output is sent.
4. Use Report-Only mode initially, since OpenCart admin and extensions commonly use inline scripts.

What is missing content security policy?

A Content Security Policy (CSP) is an instruction you send to your visitors' web browsers, embedded in a special HTTP header, that tells the browser exactly which sources of scripts, images, styles, fonts, and other content it is allowed to load on your site. Think of it as a strict guest list at a nightclub door: anything not on the list gets turned away. Without a CSP header, the browser will happily load resources from anywhere — including malicious scripts injected by attackers. Your site currently sends no CSP header at all, which means that protection layer is completely absent.

Without a CSP, your store is significantly more vulnerable to Cross-Site Scripting (XSS) attacks — one of the most common ways attackers steal customer data, hijack sessions, or install payment-skimming code (like Magecart) directly in your shoppers' browsers. A successful XSS attack can expose customers' credit card numbers, passwords, and personal information, leading to chargebacks, fines under GDPR/CCPA, PCI-DSS violations, and severe reputational damage. Google also considers site security as a ranking signal, so a visibly compromised site can lose organic search rankings fast. Adding a CSP is recognized by OWASP as a critical defense-in-depth control against injection attacks (A03:2021).

See the complete Missing content security policy guide for every platform and the full background.