Magento 2.3.3 Invalid Form Key. Please refresh page

Good day!

We recently installed an extension on our Product page to allow configurable options to show as being out of stock. this is known as the out of stock notification extension. As you may know magento as standard will hide the child options such as sizes if an child item/size is out of stock. this extension allows the size button to still display when out of stock. Once installed clicking the out of stock size option Generates a form field where the user can enter their email address, check a box to accept our privacy policy and then click a subscribe button.

It’s after clicking the subscribe button however magento generates a magento error:
Invalid Form Key. Please refresh the page.

We have contacted the developers who are leading in magento and have one of the best reputations for code quality.
Here’s their response:
The good news is that the team managed to find out what causes the problem!
We noticed that issue appears because of Lite Speed Cache module here:

With this module enabled, at the time of page load three is always the same Form Key rendered which causes the page to fail.
When we test disabled the cache, the problem went away and the module worked as expected.

So this should really be looked at from their side to learn why the pages load with the same Form Key all the time.

It would be great if at first this was attempted to be resolved from their side so that a page would not get the same Form Key.
If there is nothing to be done from their side, we can check if there is something we could do, but generally we do not debug third-party code like that.
Please let me know how it goes.

Hope someone can shed some light on this?

best wishes,


Well-Known Member
I don't know how litemage exactly works, but your description about the issue points to a missing ESI "whole" for this extension. This means litemage must be modified to support the extension from 3rd party development. To get more qualified support you should open a support ticket.