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Each HostBill is shipped with Auto-Upgrade, an enabled by default plugin that is built to make upgrades & patches easier and faster. Plugin is located under Extras->Auto-Upgrade. If its it's not enabled you can turn it on under Extras->Plugin in your HostBill Adminarea.
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Since HostBill 3.9.9 Auto-Upgrade plugin can prevent your custom files from being overwritten. If you've modified some orderpage, or use custom version of HostBill module its it's still possible to enjoy rapid upgrades, without with no need to worry about overwriting your customizations.
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When new version is available you will see notification on top of the admin home page:
After going to Extras->Auto-Upgrade you will be able to apply upgrade with one mouse click.
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A: Please refer to Before using Auto-Upgrade for the first time
Q: How to apply manually downloaded patch?
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