Common Security Risks in SVG and How to Avoid Them

SVGs are a powerful and flexible format for scalable graphics on the web. But when misused, they can introduce serious security risks. This guide walks frontend developers and designers through the most common SVG security pitfalls and practical ways to avoid them. For deeper dives and tools, check out SVGen || SVGenious and related security resources at https://svgenius.design.

Why SVGs Can be Risky

SVGs are XML-based and can contain scripts, links, and external resources. If not handled carefully, they can become a vector for cross‑site scripting (XSS), data leakage, or unintended network requests. The risk isn’t limited to inline SVGs—the way you load SVGs (inline, via <img>, <svg> embed, or <object>) matters just as much.

Common Risks and Practical Mitigations

1) Inline event handlers and script inside SVG

Embedding JavaScript directly in an SVG (for example, <svg><script> or event handlers like onclick) can execute within your page's context and open doors for XSS. Even if the SVG comes from your own server, a breach or untrusted source could inject malicious code.

Mitigation:

• Avoid inline scripts inside SVGs loaded on web pages. Prefer safe interactivity with DOM events in your main JS bundle rather than inside the SVG.
• Disable or sanitise event handlers if you must allow user-provided SVGs. Use a content policy that strips harmful attributes.
• When possible, load SVGs as <img> or <object> and keep behavior controlled by your JS code outside the SVG.

Example: avoid this pattern inside SVGs:

<svg width="100" height="100">
  <rect width="100" height="100" fill="blue" onclick="doBadThings()" />
</svg>

Safer approach: separate behavior from visuals and bind interactions in your app’s JavaScript after the SVG is loaded.

2) External resources and data leakage

SVGs can reference external resources (external images, fonts, or scripts). If an SVG references an external domain, it may cause leaks or be coerced into loading malicious content, especially if CORS or mixed content are involved.

Mitigation:

• Host SVG assets on the same domain or a trusted CDN with strict access controls.
• Prefer inline data URLs for small assets to minimize external dependencies, or pin the external resource to a known safe URL.
• Use a strict Content Security Policy (CSP) to limit what the SVG can load and execute.

Tip: if you must reference external content, validate the URLs server-side and enable subresource integrity where possible. For guidance on security-minded SVG loading, see resources at SVGenious.

3) SVGs embedded as images vs inline: differing risk surfaces

SVGs used as <img>, <svg> inlined, or via <object> all expose different risk surfaces. Inline SVGs share the page context and can access the DOM, while image-tag SVGs are more isolated but can still be manipulated in ways you don’t expect (e.g., via external resources).

Best practice:

• Use <img> for simple decorative graphics to reduce risk exposure.
• When interactivity is required, prefer importing SVGs as modular components via your frontend framework and keep scripts out of the SVG.
• Be mindful with <object> and <embed> since they can run scripts in sandboxed contexts if not configured properly.

4) External font and image resource loading

Using fonts or images referenced inside an SVG from untrusted sources can lead to unauthorized content loading or fingerprinting. Browsers may fetch fonts and images even if the SVG is not displayed by default, depending on how the SVG is used.

Mitigation:

• Host fonts locally and restrict font-face declarations within the SVG to known-safe fonts.
• Limit image loading to same-origin or trusted origins, and set image crossorigin attributes as appropriate.
• Consider inlining small assets with data URLs to avoid external requests where feasible.

5) SVG-based XSS via innerHTML or DOM parsing

Inserts of SVG markup via innerHTML or dynamic DOM parsing can introduce XSS if the content is not strictly sanitized. An attacker could inject an <svg> with harmful attributes or scripts.

Mitigation:

• Never insert user-provided SVG via innerHTML without thorough sanitization.
• Use a dedicated sanitizer that preserves acceptable SVG attributes and strips dangerous ones.
• Prefer DOM methods that operate on known-good SVG templates rather than injecting raw SVG strings.

Practical Safeguards and Best Practices

Use a strict Content Security Policy (CSP)

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