Magento 1.14.3 category page cache issues

Question

After upgrading from Magento EE 1.13 to 1.14.3.2 we have started seeing issues with category pages when full page cache is enabled.

We have a infinite scroll implementation where the next page products are loaded in an ajax call without the wrapping page markup, this is injected into the current page below the existing products. This was working fine for 1.13 but after the upgrade to 1.14 the initial page loads fine, however any subsequent page load after an ajax page shows the ajax call result, e.g it doesn't have any page layout, just the products.

Answer 1

I ended finding a couple of solutions to this problem.

Initial solution

It seems that the root of the problem is that page cache is no longer using the parameters passed to the page for its caching key, its therefore treating the content of the ajax loaded page the same as the initial load and caching over top of it. I traced this back to a new function Enterprise_PageCache_Model_Processor_Category::_filterInputParameters where the get parameter I was using, in this case p for page, was being stripped out. It seems that there is a whitelist of parameters held in $_paramsMap which are allowed, every other parameter is stripped out.

I resolved this by overriding Enterprise_PageCache_Model_Processor_Category and creating a new $_paramsMap property which contains my custom p parameter. This seems to have resolved my issue.

UPDATE - SUPEE-9465

After digging further I found this post which basically summed my issue up to a tee. It seems that there is an official Magento patch which basically just removes the _filterInputParameters function altogether. I haven't actually seen the SUPEE-9465 patch through offical Magento channels but the linked gist seems to be a legit solution.