GHSA-9mg6-x45v-hcfm activeadmin vulnerable to stored persistent cross-site scripting (XSS) in dynamic form legends

• RubyGems activeadmin: < 3.2.2 → fixed in 3.2.2 • RubyGems activeadmin: >= 4.0.0.beta1, < 4.0.0.beta7 → fixed in 4.0.0.beta7

Impact Users settings their active admin form legends dynamically may be vulnerable to stored XSS, as long as its value can be injected directly by a malicious user. For example: • A public web application allows users to create entities with arbitrary names. • Active Admin is used to administrate these entities through a private backend. • The form to edit these entities in the private backend has the following shape (note the dynamic `name` value dependent on an attribute of the `resource`): ```ruby form do |f| f.inputs name: resource.name do f.input :name f.input :description end f.actions end ``` Then a malicious user could create an entity with a payload that would get executed in the active admin administrator's browser. Both `form` blocks with an implicit or explicit name (i.e., both `form resource.name` or `form name: resource.name` would suffer from the problem), where the value of the name can be arbitrarily set by non admin users. Patches The problem has been fixed in ActiveAdmin 3.2.2 and ActiveAdmin 4.0.0.beta7. Workarounds Users can workaround this problem without upgrading by explicitly escaping the form name using an HTML escaping utility. For example: ```ruby form do |f| f.inputs name: ERB::Util.html_escape(resource.name) do f.input :name f.input :description end f.actions end ``` Upgrading is of course recommended though. References https://owasp.org/www-community/attacks/xss/#stored-xss-attacks