Many B2B SaaS tools utilize embedded Javascript widgets to collect feedback, show roadmaps, or provide customer chat support. Typically, these widgets initialize by passing the user's email address and profile context in plain text directly from the browser client.
The Identity Spoofing Risk
If a widget relies solely on plain-text email claims (e.g. userId: "usr_123") passed from the frontend, any visitor can open their browser's dev console and edit the initialization script. They can spoof another user's email, enabling them to read private changelogs, upvote roadmap items maliciously, or view confidential feedback histories.
The Solution: HMAC Verification
To prevent user spoofing, platforms must use Hash-based Message Authentication Codes (HMAC):
- Your backend server signs the user profile payload using a shared project secret key and a cryptographic hash function (such as SHA256).
- The signature is passed to the client-side widget alongside the initialization context.
- When the widget makes an API call to the widget platform, the platform's backend recalculates the signature using the shared secret. If the signatures match, the payload is verified as authentic.
Since the client doesn't know the shared secret key, they cannot forge signatures for spoofed accounts, ensuring absolute database integrity and identity safety.