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The outer parentheses defeat the grouping protection. Using the OR operator allows injection of any arbitrary regex. Now this use will reveal all times and IPs the keyword 'Bono' was searched. Using the OR operator allows injection of any arbitrary regex.
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/* Say this logfile contains:
 * CSV style: search string, time (unix), ip (integer)
 *
 * Alice,1267773881,2147651708
 * Bono,1267774881,2147651708
 * Charles,1267775881,1175563058
 *
 * and the CSVLog class has a readLine() method which retrieves a single line from the CSVLog and returns null when at EOF
 */
private CSVLog logfile;
Â
//an application repeatedly calls this function that searches through the search log for search suggestions for autocompletion
public Set<String> suggestSearches(String search)
{
  Set<String> searches = new HashSet<String>();
  Â
  //construct regex from user's string //the regex matches valid lines and the grouping characters will limit the returned regex to the search string
  String regex = "^(" + search + "),[0-9]+?,[0-9]+?$";
  Pattern p = Pattern.compile(regex);
  String s;
  while ((s = logfile.readLine()) != null) { //gets a single line from the logfile
      Matcher m = p.matcher(s);
      if (m.find()) {
          String found = m.group(1);
          searches.add(found);
      }
  }
      Â
  return searches;
}
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