Read this if disposing of an old router/modem

[#1]

Hi everyone, I’m just raising this as an ‘are you aware’ message and as something Plusnet might like to check out sometime in the future.
Some months ago we changed to FTTC and as such had a number of ADSL 2+ modem/routers become redundant.
Last week one of our family members had problems with their WiFi connections so we gave them one of the spare modem/routers to try and see if this fixed their problems.
Today I had a ‘phone call from the person setting up the unit asking for advice as he had an internet connection but was unable to get access to the router to check what was the problem.
It turned out that even after a hard factory reset all my original settings were still intact in the modem, the worrying thing was He was logged in using my old details to Plusnet while I was simultaneously logged in on FTTC. Should this be possible and does this raise implications for disposal of old routers and the ability of factory resets to erase all old data stored in them.
I was lucky this was a family member as all my old login details (which I also use for FTTC) was visible to him and I had to talk him through erasing and changing everything to his BT credentials so he could connect correctly.

[#2]

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It turned out that even after a hard factory reset all my original settings were still intact in the modem,

Plusnet routers have the facility to autoconfigure using TR-069. A factory reset will have returned the router to the default TR069 login. However, the router is registered to your account, so the autoconfigure willl automatically put your username/password back in, although I'm surprised that it works on a BT provisioned line.
What you should do when passing on a PlusNet router, is request that it is deregistered from your account, and then factory reset it.

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He was logged in using my old details to Plusnet while I was simultaneously logged in on FTTC. Should this be possible

That's perfectly possible UNLESS your account has a static IP. In the normal case of dynamic IP both routers will be allocated different IP addresses and so will work fine.

[#3]

It sounds like the TR69 details are still registered on the router logged to you. I can easily remove these for you if you like.
Just so I've doing the right details, please confirm which router it is and I'll get onto it. The first four characters of the serial number (including the CP) will be enough).