CSV Injection

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CSV Injection, also known as Formula Injection, occurs when websites embed untrusted input inside CSV files.

When a spreadsheet program such as Microsoft Excel or LibreOffice Calc is used to open a CSV, any cells starting with ‘=’ will be interpreted by the software as a formula. Maliciously crafted formulas can be used for three key attacks:

  • Hijacking the user’s computer by exploiting vulnerabilities in the spreadsheet software, such as CVE-2014-3524
  • Hijacking the user’s computer by exploiting the user’s tendency to ignore security warnings in spreadsheets that they downloaded from their own website
  • Exfiltrating contents from the spreadsheet, or other open spreadsheets.

This attack is difficult to mitigate, and explicitly disallowed from quite a few bug bounty programs. To remediate it, ensure that no cells begin with any of the following characters:

  • Equals to (“=”)
  • Plus (“+”)
  • Minus (“-“)
  • At (“@”)

For further information, please refer to the following articles: