Ontinue Uncovers SVG-Based Phishing: Why Your Browser Could Be the Weak Link

Daily Security Review

Ontinue has uncovered a stealthy new phishing campaign that’s flipping conventional defenses on their head—weaponizing SVG image files to silently redirect victims to malicious websites, without requiring file downloads, macros, or even user clicks.

In this episode, we break down how attackers are exploiting the JavaScript-capable structure of Scalable Vector Graphics (SVG) to embed obfuscated scripts that decrypt malicious payloads directly in the browser at runtime. These files are being distributed via spoofed emails with weak sender authentication, evading traditional detection tools by masquerading as innocuous graphics—when in fact, they’re functioning like client-side malware.

Key topics include:

• How SVGs bypass legacy email security through script execution in the browser
• The role of JavaScript obfuscation and DOM manipulation in these attacks
• Why this approach is ideal for credential harvesting and phishing-as-a-service
• How weak SPF, DKIM, and DMARC records enable spoofing at scale
• Mitigation strategies: From treating SVGs as executables to enforcing strict CSP headers, Safe Links rewriting, and layered email authentication

We also explore the broader implications of this trend within the phishing landscape—how attackers are moving away from traditional malware delivery toward zero-download, browser-native exploitation. This evolution makes every user’s browser session a potential threat surface and highlights the urgent need for both technical controls and human-centric awareness training.

Ontinue’s discovery reinforces a core truth in modern cybersecurity: “innocent” file types can no longer be assumed harmless, and phishing tactics are increasingly blending code, content, and clever evasion. If your organization handles external emails, especially in B2B services, this episode is a critical briefing on a quiet but powerful threat.