This is known as popunder and we have protections in place to prevent popunders. Your report is no bug in the product and as an enhancement requests it's a wontfix because i don't know a reason why a normal user would want a feature like this. In case you need this feature for your own firefox installation you should consider writing an addon.
Status: UNCONFIRMED → RESOLVED
Last Resolved: 4 years ago
Resolution: --- → WONTFIX
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