Heym before 0.0.53 fails to verify Slack request signatures when trigger nodes lack credential IDs or have empty signing secrets. Remote unauthenticated attackers can send forged Slack events to known webhook URLs to trigger workflows with the owner's credentials.

Heym before 0.0.53 fails to verify the X-Telegram-Bot-Api-Secret-Token header on Telegram webhook endpoints when credentialid is absent or secrettoken is empty. Remote unauthenticated attackers can post forged Telegram updates to trigger workflows with the owner's configured credentials and execute actions on attacker-supplied input.

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 versions 0.0.90 and earlier contain two server-side request forgery (SSRF) egress gaps, both remediated in app/services/ssrfguard.py in 0.0.91. First, the LLM image-edit input loader (loadimagebytes) fetched caller-controlled HTTP/HTTPS URLs with a bare httpx.get, applying only a scheme check and bypassing the egress-pinning HTTP client; because the workflow DSL supports "imageInput": "$userInput.body.imageUrl", a webhook or API caller can choose the fetch target when a workflow author uses that expression, allowing requests to loopback, RFC1918, and cloud metadata endpoints. Second, ispublicaddress unwrapped only IPv4-mapped IPv6 addresses, so IPv6 transition forms — the NAT64 well-known prefix 64:ff9b::/96, deprecated IPv4-compatible ::x.x.x.x addresses, and 6to4 (2002::/16, classified as globally routable by Python 3.11.0 through 3.11.9) — could carry loopback, RFC1918, link-local, or cloud-metadata IPv4 destinations past both the initial URL validation and the dial-time IP pin. Version 0.0.91 routes the image loader through guardhttpurl and the guarded client, evaluates NAT64 and IPv4-compatible addresses by their embedded IPv4 address, and refuses 64:ff9b:1::/48, 6to4, and Teredo (2001::/32) outright.

heym, a workflow automation platform, stores and returns multiple capability secrets in plaintext in versions prior to 0.0.91. Affected secrets include webhook header-auth values (returned in cleartext by GET /api/workflows/{id} and persisted unsanitized into execution history), MCP API keys (stored as a plaintext column, returned in config/list responses, and accepted via the ?key= query string so they leak into logs, proxies and Referer headers), portal session tokens (stored and validated by plaintext equality with a 168-hour TTL), workflow execution JWTs (stored in full and re-listed by GET .../execution-tokens), Discord interaction tokens (the full interaction body is stored in execution history), and global variables. A user with read access to a workflow, share/team membership, or anyone able to read the database, a backup, or logs can recover these secrets and replay them to execute workflows or act as the secret owner.

Heym before 0.0.106 contains a credential exfiltration vulnerability in the POST /api/credentials/test endpoint that allows collaborators with shared credential access to exfiltrate the credential owner's secret. Attackers can override the destination URL in the config parameter to cause the server to send decrypted authentication secrets to attacker-controlled endpoints.

heym before 0.0.109 contains a server-side request forgery vulnerability in the Slack, Discord, and Crawler workflow nodes. These nodes issue HTTP requests to URLs taken from user-created credentials (webhookurl / flaresolverrurl) using an unguarded HTTP client, bypassing the SSRF egress guard that already protects the HTTP, WebSocket, and MCP nodes; the credential API validates only that the URL is non-empty. Any registered user can create a credential pointing at an internal address and execute a workflow, causing the backend to reach loopback, private, link-local, or cloud-metadata endpoints and return the full response body in the node output (non-blind SSRF).