#3 Founder's letter: Our first prompt injection attempt
Published: February 27, 2026
·1 min readYesterday Bankstatemently saw its first real prompt injection attempt in production.
A user uploaded what looked like a normal Chase (US) bank statement with five legitimate transactions.
But at the very bottom of the PDF was a block of text attempting to override system instructions and extract internal configuration details.
How the system handled it
- The model ignored the injected instructions
- Our pipeline independently detected and flagged the manipulation attempt
- The document was processed normally
- No system prompts, API keys, or environment data were exposed
Bankstatemently is financial infrastructure. Every document is treated as untrusted input, and the system is built accordingly.
Adversarial input is part of operating real systems. It's a thankful reminder to keep hardening.
Building in public, one statement at a time.
Michael · Bankstatemently
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