YesWiki: Second-Order SQL Injection in Page Delete API via Unescaped Page Tag (ApiController::deletePage)
Summary
ApiController::deletePage() interpolates a page tag retrieved from the database into a DELETE FROM …_links WHERE to_tag = '$tag' query without escaping. The page tag is attacker-controlled — the POST /api/pages/{tag} API accepts arbitrary URL-encoded values, including single quotes, and stores them. A low-privilege authenticated user can therefore create a page whose tag is a SQL fragment, make the page non-orphaned via the standard {{include page="…"}} link mechanism, and then invoke the delete endpoint to execute arbitrary SQL inside the wiki database - including time-based blind data exfiltration from any table.
This is a classic second-order SQL injection: the INSERT correctly escapes the value, so the malicious tag is stored intact and the input passes every "is this value safe to put in the database?" check; the sink is the *read-back-and-reuse* path, where escaping is omitted.
Details
Affected component
- File:
includes/controllers/ApiController.php - Method:
ApiController::deletePage($tag) - Route:
@Route("/api/pages/{tag}", methods={"DELETE"}, options={"acl":{"+"}}) — acl:"+" means *any authenticated user*. - Sink: line 626
```php
// includes/controllers/ApiController.php (v4.6.5 = origin/doryphore-dev HEAD,
// lines 607–631)
public function deletePage($tag)
{
$pageManager = $this->getService(PageManager::class);
$pageController = $this->getService(PageController::class);
$dbService = $this->getService(DbService::class);
...
try {
$page = $pageManager->getOne($tag, null, false); // (a) safe SELECT
if (empty($page)) { ... } else {
$tag = isset($page['tag']) ? $page['tag'] : $tag;// ^ raw tag from DB
$result['notDeleted'] = [$tag];
if ($this->wiki->UserIsOwner($tag) || $this->wiki->UserIsAdmin()) {
if (!$pageManager->isOrphaned($tag)) {
$dbService->query(
"DELETE FROM {$dbService->prefixTable('links')}
WHERE to_tag = '$tag'"); // (b) SINK — unescaped
}
...
```
The same anti-pattern shows up in two adjacent files; both were noted in the original submission and confirmed during validation:
tools/tags/handlers/page/__deletepage.php line 14 - DELETE … WHERE to_tag = '$tag', where $tag = $this->GetPageTag() is again the raw stored tag.handlers/page/deletepage.php lines 93–94 - LoadAll('SELECT DISTINCT from_tag FROM …links WHERE to_tag = '" . $this->GetPageTag() . "'"), same pattern as a SELECT instead of a DELETE.
The API path is the easiest sink to reach because it requires only acl:"+" and a single HTTP request; the other two require a logged-in user to navigate to the page's delete handler
A low-privilege account can carry the whole chain:
1. Plant — POST /api/pages/{evil} with body=anything. PageManager::save() escapes the tag at INSERT time ('\'' in SQL ⇒ stored '), so the tag persists with its single quote intact. The new page is owned by the attacker, so UserIsOwner($tag) in the delete handler will return true.
2. Make non-orphaned — save *any* second page whose body contains {{include page="<evil>"}} through the web edit handler. LinkTracker::preventTrackingActions() parses the include directive, looks up the referenced page (PageManager::getOne() finds it because lookup uses escape(), which matches the stored quote), and LinkTracker::persist() inserts a row (from_tag='Linker', to_tag='<evil>') into _links — again with escape() on the way in, so the raw quote round-trips.
3. Trigger — DELETE /api/pages/{evil}. The delete handler reads the page (escaped SELECT, finds the row), assigns $tag = $page['tag'] (the raw stored value, including '), runs isOrphaned($tag) (escaped SELECT, returns *not* orphaned because step 2 inserted a row), and then runs the unescaped DELETE FROM …_links WHERE to_tag = '$tag'. The SQL parser sees the attacker-controlled ' as the end of the string literal; everything after it is treated as SQL.
The injection point is WHERE to_tag = '<here>' — any payload of the form <anything>' <SQL>-- works. With time-based primitives (SLEEP), the attacker reads any byte of any row of any table the wiki account can see.
End to End Steps to reproduce the issue
1. Preflight
- lab is up at http://localhost:8085
2. Logging in
- admin 'WikiAdmin' and low-priv 'TestUser01' both logged in
3. Tier 1 - POST /api/pages/<evil-tag> (as TestUser01)
- PROOF: tag stored RAW in yeswiki_pages → 'SleepTag' OR SLEEP(2)-- '
4. Tier 2 - make the evil page non-orphaned
- PROOF: yeswiki_links row → LinkPoc->SleepTag' OR SLEEP(2)--
5. Tier 2 - DELETE /api/pages/<evil-tag> (as TestUser01)
- baseline (non-existent tag) : 0.468s
