Webhook notifications fail with "[object Object] is not valid JSON" after saving via API/UI

[aldoeliacim]

Bug Description

Webhook notifications fail silently with the error:

Error sending webhook notification {"type":"MEDIA_AVAILABLE","subject":"...","errorMessage":"\"[object Object]\" is not valid JSON"}

This affects any webhook configuration saved through the API or UI. The default webhook payload works correctly because it is hardcoded as a double-encoded base64 string, but user-customized payloads break immediately.

Root Cause

In server/lib/notifications/agents/webhook.ts, buildPayload() double-parses the stored JSON payload:

const parsedJSON = JSON.parse(JSON.parse(payloadString));

This expects the base64-decoded string to be a JSON-encoded string (i.e., a string value that itself contains JSON). The first JSON.parse unwraps the outer string, and the second parses the inner JSON.

However, the save routes in server/routes/settings/notifications.ts (POST /webhook and POST /webhook/test) only single-encode:

jsonPayload: Buffer.from(req.body.options.jsonPayload).toString("base64")

This stores the raw JSON string directly in base64. When buildPayload double-parses it:

1. First JSON.parse: parses the JSON string → produces a JS object
2. Second JSON.parse: calls .toString() on the object → "[object Object]" → fails

Steps to Reproduce

1. Go to Settings → Notifications → Webhook
2. Configure a webhook URL and save (with any JSON payload)
3. Click "Test" or trigger any notification (media request, approval, etc.)
4. Check logs: "[object Object]" is not valid JSON

Expected Behavior

Webhook notifications should be sent successfully after saving via the UI/API.

Fix

The save routes should wrap the payload with JSON.stringify() before base64-encoding, matching the double-encoded format that buildPayload expects:

jsonPayload: Buffer.from(JSON.stringify(req.body.options.jsonPayload)).toString("base64")

PR: #(incoming)

Environment

• Seerr version: 3.1.0 (also present in current develop branch)
• Affects: all webhook configurations saved via API/UI