A security issue has been identified that affects versions 8.5 and 8.6 of WHMCS.
As a result, we have published new releases of WHMCS 8.5 and 8.6. All earlier versions of WHMCS are unaffected.
The issue was reported privately and there is no evidence to suggest it is known publicly. We will not be releasing any further details about the issue at this time.
What should I do?
You should update WHMCS, either manually or using the Automatic Updater, as soon as possible. We recommend using the Automatic Updater. Update Instructions
Automatic Update Steps- Login to your WHMCS Admin Area.
- Navigate to Utilities > Update WHMCS.
- Click Check Now to check for updates. When the check completes you will see a new version is available.
- Click the Update Now button and follow the wizard based steps.
You may reference the Automatic Updater for more a detailed description of the update utility. Likewise, you may reference our article on Updating for more in-depth guidance.
Manual Update Steps
- Visit https://download.whmcs.com/
- If you are running the immediately preceding version, you can update using the Incremental Patch Set. Select this tab and then choose the appropriate patch for your given version.
- If you are running any earlier version of WHMCS, you will need to download and update using the full release package for your desired version.
- Once you have downloaded the appropriate update file, follow the steps within the Readme file to perform the update process.
What is included in the update?
The update includes a resolution for the security issue as well as important maintenance fixes related to that version of WHMCS. You can review the respective changes at the following changelog locations: Need Help?
If you have any issues updating your WHMCS installation or applying the patch, you can contact our support team at www.whmcs.com/submit-a-ticket 
