Image Upload issue after PATCH 8788 install on 1.9.2.4

I was able to fix it,Please Follow following instruction.

Step >> 1: After installed security patch 8788 successfully, Please go to admin panel and flush all Magento cache. Then Logout your Admin Panel and Relogin to Admin Panel.

Step >> 2: Go to Index Management and select all reindex all data after flush all Magento cache once again.

Step >> 3: This very Important step, Delete your browser cache(Ctrl+shift+Delete) history clear all browsing data from browser including cookies.

Step >> 4: Go to Catalog >> Product Management , add new image of any product,now you can see everything work fine.

I had this same problem, on same version of Magento CE 1.9.2.4. I was able to fix it by flushing my Magento cache (everything), then refreshing the cache (everything), then flush our CDN cache (cloudflare), then clear all browsing data from browser including cookies.

Please note that until I remembered to flush our CDN cache, our local Magento cache refresh didn't fix the problem.

Once everything was flushed and refreshed, the image uploader worked just fine.

I got the idea for this fix over on the magento community forums: https://community.magento.com/t5/Security-Patches/SUPEE-8788-Can-t-upload-images-in-product-after-patch-has-been/m-p/50463#U50463

(see onlinestore23's post half way down 1st page)

Good luck!