# `Assent.Strategy.CallbackCSRFError`
[🔗](https://github.com/pow-auth/assent/blob/v0.4.0/lib/assent/strategy.ex#L63)

An exception for when callback CSRF validation fails.

## Fields

  * `:key` - the callback parameter that failed validation

## Examples

    iex> error = Assent.Strategy.CallbackCSRFError.exception(key: "state")
    iex> Exception.message(error)
    "expected callback parameter `state` to match its value in session params"

# `t`

```elixir
@type t() :: %Assent.Strategy.CallbackCSRFError{__exception__: term(), key: binary()}
```

# `message`

---

*Consult [api-reference.md](api-reference.md) for complete listing*