$ cat > json
[{
  "values": [
    {
      "skip_ssl_validation": false
    }
  ],
  "default": false,
  "example": null
}]
$ cat json | jq --arg k skip_ssl_validation '(.[]| select(.values[]|has($k)).default) |= true'
jq: error (at <stdin>:8): Invalid path expression near attempt to access element "default" of {"values":[{"skip_ssl_vali...
$ cat json | jq --arg k skip_ssl_validation '(.[]| select(.values[]|has($k)).default)'
false