CVE-2026-52763

### 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. ```php 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