The Crayons plugin for SPIP before 3.5.0 contains a missing authorization vulnerability that allows unauthenticated attackers to modify arbitrary editable object fields by omitting the secu anti-forgery parameter in crayonsstore.php, causing the authorization dispatcher to resolve an unconditionally-true handler instead of the proper modification check. Attackers can chain this flaw to write a malicious .html skeleton file, disclose sensitive configuration files containing the site secret, and forge a signed ajax context to execute the uploaded skeleton, achieving arbitrary PHP code execution as the web-server user.