If it’s a bulb with a battery back-up (or possibly even if it’s not), the switch(es) may not be wired properly for it. If the switch breaks the neutral instead of the hot, it might keep it on. Probably need an electrician to sort it out.
My best guess would be that there is a little bit of current running through your sockets and your new bulb requires so little current that it’s enough to produce light. Completely unexpected guess though
Own-Cupcake7586 t1_j2escc4 wrote
If it’s a bulb with a battery back-up (or possibly even if it’s not), the switch(es) may not be wired properly for it. If the switch breaks the neutral instead of the hot, it might keep it on. Probably need an electrician to sort it out.