Improper Neutralization of Formula Elements in a CSV File

Many applications export data to CSV files for easy viewing in spreadsheet software. However, these programs treat cells beginning with characters like =, +, -, or @ as formulas. If an attacker can inject data like `=HYPERLINK("http://malicious-site.com", "Click")` or a formula that calls external scripts, simply opening the CSV file can trigger data theft, remote code execution, or other harmful actions on the user's machine. Developers often overlook this risk because CSV files are seen as simple data dumps, not executable content. To prevent this, you must sanitize or escape formula-initiating characters in all user-controlled fields before writing them to a CSV. This ensures that data is displayed as static text, not as an active command, when the file is imported into a spreadsheet application.