CVE-2026-54366: Improper Restriction of XML External Entity Reference

CentreStack before 17.4 contains an XML external entity (XXE) injection vulnerability that allows unauthenticated attackers to exfiltrate arbitrary files by supplying a malicious URL to the SharePoint storage configuration handler. Attackers can send a crafted request to the unauthenticated StorageConfig endpoint causing the server to fetch and parse attacker-controlled XML containing external DTD references, resulting in out-of-band file exfiltration of sensitive files such as Web.config, which may contain database credentials and cryptographic key material.