Heym before 0.0.53 evaluates workflow condition expressions using Python's eval() with insufficient sandboxing in the workflow executor service. Authenticated users can edit workflow condition nodes or import malicious templates to execute arbitrary Python and OS commands as the backend process user.

Heym before 0.0.53 contains multiple independent vulnerabilities. (1) The workflow condition evaluator uses Python eval() without an effective sandbox, allowing any user who can edit a workflow branch/condition node — or who can import a workflow template containing a malicious condition node — to execute arbitrary Python code as the backend process user when the workflow runs. (2) Slack webhook signature verification and (3) Telegram webhook secret-token verification fail open when the trigger node has no credentialId or an empty signing secret, allowing anyone who knows the public webhook URL to trigger workflows with the owner's credentials without authentication. (4) The OAuth authorization endpoint does not validate the redirect_uri scheme, so an attacker who registers a public OAuth client with a javascript: or data: redirect_uri and lures a victim to the consent screen receives the authorization code and executes attacker-controlled JavaScript in the Heym origin, including access to the victim's HttpOnly auth cookie. (5) WorkflowExecutionToken, PortalSession, HITLRequest.public_token, and OAuthAuthorizationCode values are stored in plaintext, so any database read exposure yields valid scoped bearer tokens, including portal and HITL tokens with a 168-hour TTL that permit workflow execution on behalf of the owner.