Spreadsheet prompt injection risk

Finance teams often receive spreadsheets from suppliers, customers and partners. If an AI tool reads the workbook, hidden instructions or misleading notes can shape the answer. The safe stance is to treat external spreadsheets as untrusted input.

Practical SME workflow

Use an invoice exception review workflow with a clean intake step. Strip irrelevant tabs, keep source files separate and ask AI to inspect data fields only. Supplier wording and payment actions stay with finance.

Risk and control

Use a copy of the workbook, keep the original, and ask for cited cells or source references where the tool supports them. Do not let generated instructions inside the sheet override your own policy, approval route or data boundary.

Source basis

• Anthropic: Use Claude for Excel
• OpenAI: ChatGPT for Excel and Google Sheets