system/Filters/CSRF.php
public function before(RequestInterface $request)
	{
		if ($request->isCLI())
		{
			return;
		}

		$security = Services::security();

		try
		{
			$security->CSRFVerify($request);
		}
		catch (SecurityException $e)
		{
			if (config('App')->CSRFRedirect && ! $request->isAJAX())
			{
				return redirect()->back()->with('error', $e->getMessage());
			}

			throw $e;
		}
	}
public function before(RequestInterface $request)
	{
		if ($request->isCLI())
		{
			return;
		}

		$security = Services::security();

		try
		{
			$security->CSRFVerify($request);
		}
		catch (SecurityException $e)
		{
			if (config('App')->CSRFRedirect && ! $request->isAJAX())
			{
				return redirect()->back()->with('error', $e->getMessage());
			}

			throw $e;
		}
	}
Do whatever processing this filter needs to do.
By default it should not return anything during
normal execution. However, when an abnormal state
is found, it should return an instance of
CodeIgniter\HTTP\Response. If it does, script
execution will end and that Response will be
sent back to the client, allowing for error pages,
redirects, etc.

@param RequestInterface|\CodeIgniter\HTTP\IncomingRequest $request

@return mixed