YesWiki: SQL injection via the `recentchanges` action `period` argument leads to arbitrary DB read

Summary

The recentchanges action (actions/recentchanges.php) accepts a period argument from two disjoint parameter spaces: the URL query string ($_GET['period']) and the action invocation {{recentchanges period="..."}}. A whitelist at line 17 validates only the URL form against ['day','week','month']. The action-argument form takes the else branch at line 33 ($dateMin = $this->GetParameter('period')) with no validation, and the value flows into PageManager::getRecentlyChanged() (includes/services/PageManager.php:196), where it is interpolated into a WHERE time >= '...' ORDER BY time DESC clause without escaping or parameterization. UNION-based injection succeeds, the leaked rows render into the response page via actions/recentchanges.php:43,58 (ComposeLinkToPage($page['tag'])), so any visitor of the trigger page sees the exfiltrated data.

The vulnerability provides arbitrary read of the YesWiki database to anyone who can save the trigger page. On a default install (default_write_acl='*'), this includes anonymous users, subject to the hashcash JS check on the page-edit form. Once the trigger page is saved, every subsequent view fires the injection as the SQLi is stored. Stored SQL injection is reachable through the page-edit flow, with arbitrary database read.

Details

Two issues compose the vulnerability.

1. actions/recentchanges.php line 33 reads the action argument and skips the whitelist.

   if (isset($_GET['period']) && in_array($_GET['period'], ['day', 'week', 'month'])) {
       switch ($_GET['period']) {
           case 'day':   $d = strtotime('-1 day');   $dateMin = date('Y-m-d H:i:s', $d); break;
           case 'week':  $d = strtotime('-1 week');  $dateMin = date('Y-m-d H:i:s', $d); break;
           case 'month': $d = strtotime('-1 month'); $dateMin = date('Y-m-d H:i:s', $d); break;
       }
   } else {
       $dateMin = $this->GetParameter('period');   
   }
   

   Wiki::GetParameter() (includes/YesWiki.php:895) reads $this->parameter[$key], which is populated from the {{action key=value}} argument list — disjoint from $_GET. The whitelist's if branch only runs when $_GET['period'] matches one of three exact values; in every other case the else branch reads the action argument with no validation, no escaping, no DateTime parse, no regex. The two parameter spaces are independent.