spelling: verification

Signed-off-by: Josh Soref <jsoref@users.noreply.github.com>

Author: jsoref

attack/file-upload/README.md

@@ -4,7 +4,7 @@ see:  http://cwe.mitre.org/data/definitions/434.html
 
 * kinds of file upload verifications:
  * content-type
- * filename extension verificationi (whitelist, blacklist)
+ * filename extension verification (whitelist, blacklist)
  * file content checking
  * client side, ha ha ha