fix(posthog): reject unsafe self-hosted host values (SSRF)

The self-hosted host field accepted any string and only stripped
trailing slashes before prepending https://, so a workflow could point
it at loopback/private/link-local addresses (e.g. cloud instance-
metadata endpoints) and the executor would make a real server-side
request to it. Reuse the shared validateExternalUrl SSRF guard, same
pattern already used for Convex's custom deployment URL
(tools/convex/utils.ts); the tool executor separately re-validates with
DNS resolution and pins the resolved IP for the actual request.

Also drop an unused params arg in evaluate_flags' headers function.

Author: waleedlatif1

apps/sim/tools/posthog/evaluate_flags.ts

@@ -80,7 +80,7 @@ export const evaluateFlagsTool: ToolConfig<EvaluateFlagsParams, EvaluateFlagsRes
       return `${baseUrl}/flags/?v=2`
     },
     method: 'POST',
-    headers: (params) => ({
+    headers: () => ({
       'Content-Type': 'application/json',
     }),
     body: (params) => {

apps/sim/tools/posthog/utils.ts

@@ -1,3 +1,5 @@
+import { validateExternalUrl } from '@/lib/core/security/input-validation'
+
 /**
  * Shared PostHog base URL resolution.
  *
@@ -7,7 +9,10 @@
  * - The "ingest" API (`/i/v0/e`, `/batch/`, `/flags/`) at `us.i.posthog.com` / `eu.i.posthog.com`,
  *   authenticated with a project API key.
  *
- * Self-hosted PostHog instances serve both families from a single custom host.
+ * Self-hosted PostHog instances serve both families from a single custom host. That host is
+ * validated with the shared SSRF guard so it can't be pointed at loopback/private/link-local
+ * addresses (e.g. cloud instance-metadata endpoints); the tool executor additionally
+ * re-validates with DNS resolution and pins the resolved IP for the actual request.
  */
 
 export function getPostHogAppBaseUrl(region?: 'us' | 'eu', host?: string): string {
@@ -26,5 +31,10 @@ export function getPostHogIngestBaseUrl(region?: 'us' | 'eu', host?: string): st
 
 function normalizeHost(host: string): string {
   const trimmed = host.trim().replace(/\/+$/, '')
-  return /^https?:\/\//i.test(trimmed) ? trimmed : `https://${trimmed}`
+  const withProtocol = /^https?:\/\//i.test(trimmed) ? trimmed : `https://${trimmed}`
+  const validation = validateExternalUrl(withProtocol, 'Self-hosted host')
+  if (!validation.isValid) {
+    throw new Error(`${validation.error} (e.g., posthog.mycompany.com)`)
+  }
+  return withProtocol
 }