Seeing `invalid signature: the signature value`...`is incorrect`

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We ran across:

{
  "date": "2026-06-11T05:50:14.771Z",
  "type": "flo",
  "description": "invalid signature: the signature value ...== is incorrect",
  "connection_id": "",
  "client_id": "...",
  "client_name": "...",
  "ip": "...",
  "user_agent": "Edge 149.0.0 / Windows 10.0.0",
  "details": {
    "allowed_logout_url": []
  },
  "hostname": "...",
  "user_id": "",
  "user_name": "",
  "location_info": {
    ...
  },
  "$event_schema": {
    "version": "1.0.0"
  },
  "environment_name": "prod-us-1",
  "log_id": "90020260611055014807412000000000000001223372175632636094",
  "tenant_name": "...",
  "_id": "90020260611055014807412000000000000001223372175632636094",
  "isMobile": false,
  "id": "90020260611055014807412000000000000001223372175632636094"
}

There were a couple of other old posts about invalid signatures, but they didn’t say much. I’m leaving this here mostly so others can see it’s a thing.

As this is logout as opposed to login, I don’t think this is an attacker sending random garbage (it’s a real user; and they’re using our frontend which uses GitHub - auth0/auth0.js: Auth0 headless browser sdk · GitHub to manage things).