The ACME-challenge endpoint in Appwrite 0.5.0 through 0.12.x before 0.12.2 allows remote attackers to read arbitrary local files via ../ directory traversal. In order to be vulnerable, APP_STORAGE_CERTIFICATES/.well-known/acme-challenge must exist on disk. (This pathname is automatically created if the user chooses to install Lets Encrypt certificates via Appwrite.)