New SUPEE-8788v2 patch can be downloaded as usual from Downloads page:
https://www.magentocommerce.com/products/downloads/magento/ or installed as a regular Magento upgrade via Downloader (it is included in Magento 1.9.3 version).

You can install it in the same way as previous patches or by upgrading to Magento 1.9.3.

To apply the patch you need SSH access (shell access actually, SSH is just most used way to get shell access) to the server. If you have no SSH access, you can refer to How to apply SUPEE-7405 without SSH.

If you wish to save time and have us to install these patches for you, simply click here to order installation.

Step 0: Preparations

Note: Make sure to Disable Magento Compiler at System > Configuration > Tools > Magento Compiler and clear compiled cache.

Step 1: Verify your Magento version

$ grep -A6 'static function getVersionInfo' app/Mage.php
    public static function getVersionInfo()
    {
        return array(
            'major'     => '1',
            'minor'     => '9',
            'revision'  => '2',
            'patch'     => '4',

As you can see in the example, it is Magento 1.9.2.4

Step 2: Download corresponding patches

Patches are obtained from https://www.magentocommerce.com/products/downloads/magento/

Make sure to get the right version.

Step 3: Place patches into Magento Root directory

Upload your files into Magento root directory. It is important to place patch files directly into Magento root directory and execute it also directly in Magento root directory.

$ ls -1 .
PATCH_SUPEE-8788_CE_1.9.2.4_v2-2016-10-14-09-42-47.sh
app
cron.php
downloader
errors
favicon.ico
index.php
js
lib
mage
media
pkginfo
robots.txt
shell
skin
var

 

Step 4: Run the patches

$ bash PATCH_SUPEE-8788_CE_1.9.2.4_v1-2016-10-11-07-03-46.sh
Checking if patch can be applied/reverted successfully...
Patch was applied/reverted successfully.

Step 5: Verification and flush of PHP opcode cache

Test that your store is working. If you use PHP opcode caches (OPCache/APC/XCache/eAccelerator) make sure to flush it after patching (or restart webserver), otherwise code will continue to run from caches.

Additionally, if your store still use default /admin/ path, you may consider restrict access to /downloader/.

Known issues

Product image upload is broken by CreareSEO extension

Product image upload is broken by CreareSEO extension

Edit product page is broken in backend

Edit product page is broken at Catalog > Manage Products > Edit product page

Hunk #1 FAILED at 91 for app/code/core/Mage/Adminhtml/controllers/DashboardController.php
Hunk #1 FAILED at 91.
1 out of 1 hunk FAILED -- saving rejects to file app/code/core/Mage/Adminhtml/controllers/DashboardController.php.rej

The issue is caused by conflict with changes from SUPEE-1533. You need to revert SUPEE-1533 patch. Please make sure also that you are installing SUPEE-8788v2 version re-uploaded by Magento on October 15. Alternatively, you can apply patch by direct file upload as shown in How to install SUPEE-8788 without SSH.

Hunk #1 FAILED at 372 for downloader/lib/Mage/HTTP/Client/Curl.php
Hunk #1 FAILED at 372.
1 out of 1 hunk FAILED -- saving rejects to file downloader/lib/Mage/HTTP/Client/Curl.php.rej

The issue is caused by dependency on SUPEE-3941 patch. You need to apply SUPEE-3941 patch. Please make sure also that you are installing SUPEE-8788v2 version re-uploaded by Magento on October 15. Alternatively, you can apply patch by direct file upload as shown in How to install SUPEE-8788 without SSH.