App does not appear in Firefox

Some pre-Aragon 0.6 apps do not load in newer versions of the Firefox browser. When the user visits these apps, they show up as blank pages like this:
To fix this error in your organization, you have to update the app version of the app that is showing up blank to a newer version of the app using the App Center.
If the Voting app is one of the apps affected by this problem, and you need to approve a vote to complete the app update, then you have to use either the in-client Console or aragonCLI to vote on the App Upgrade proposal.