such an error periodically comes out, we cannot understand what it is the reason.
but after 2-3 minutes it disappears, and the login is done successfully, but after leaving the profile, you can’t go back, this error appears again

Facebook SDK returned an error: Cross-site request forgery validation failed. The "state" param from the URL and session do not match.

I got this error once as well, then never again.

Its looks like the problem is in the code,

Found this in one forum,

There could be 2 reason for this error:

you didn't call session_start(); before getLoginUrl call
You executed getLoginUrl again in login-callback.php, so state value regenerated and mismatched with the redirected value

and

I had the same problem.

The reason for this error is because --->

When "$helper->getLoginUrl" calls, it create a session variable "FB_State", and this is something to FB uses to match the token. Every-time getLoginUrl calls, it create new state. Then after user authorized and redirect back, if you codes cannot detect this event and re-run "$helper->getLoginUrl", then this error will occur.

The solution ->

refine your coding, stop run "$helper->getLoginUrl" again if authorized.

if you already rerun, then set the session variable for the token to NULL if you have, then User can re-authorize again.

when user tries re-authorize, they can remove the authorized APP once or you need to generate new link with "$helper->getReRequestUrl"

Yet, token has be called by "getAccessToken()" before the "$helper->getLoginUrl" or "$helper->getReRequestUrl" runs.

Good Luck!!!!!

@MbThemes, maybe you can help with that

@MbThemes,

the reason of this issue is cache plug-in, When I turn off the cache on the home page, fb login plugin working properly and without errors. As soon as I turn ON cache on Home page, this message appears.

I hope that you look at the possibility of correcting this error.

Thanks

That is strange, plugin should disable cache when fb login request is coming

I'm facing the same problem, And i dont have cache plugin! any advice?

I found this solution to fix it guys we need to insert below code after $helper = $fb->getRedirectLoginHelper();

if (isset($_GET['state'])) {
    $helper->getPersistentDataHandler()->set('state', $_GET['state']);
}

Read more at:

https://stackoverflow.com/questions/32029116/facebook-sdk-returned-an-error-cross-site-request-forgery-validation-failed-th