TLDR; 2 years ago when I am still using Streamyx and DLink router, occasionally I will see random Mac address shows up on DHCP table.
Model: DSL-2877AL

So discovered there is always a random weird devices show up on the DHCP table.
I am 100% sure these are not my devices and I don't have repeater, access point, cctv or neither Huawei phone at that time.
Usually something like this from the table.

android-24fcc788014831d8 54:27:58:E5:23:32
HUAWEI_Y7_Prime 8C:25:05:A2:B2:BF
dlinkap EC:22:80:E3:98:44
Tenda F4:F2:6D:31:2A:26
android?? 00:9F:AC:6E:06:27

Sometimes this
android-b82f2e73852163e0 9C:5C:F9:4A:72:41

No matter what I did, it just keeps showing random devices on DHCP table even after I blocked it, a new random device will show up.
1. I'm using WPA2-AES and extremely complex pw.
2. Only allow whitelist Mac address.
3. Block suspicious Mac address.

I've also contacted DLink via FB to check with them whether the model was vulnerable because of this bug.
They told me HQ confirmed that we are not affected from this.
https://www.bleepingcomputer.com/news/secur...lose-passwords/

After I switch to TP-Link, the issue is gone.
Until today, it still puzzles me, whether my network was compromised, or this router did some fishy stuff on the backend.
Any networking expert able to explain this?

Did you disable WPS?
If no, then that's the answer to your question

WPS on some routers is easily hackable

I don't rmb I ever configure WPS, it should be default. So not sure, it's enable or disable.

Most routers enabled them by default

Are you using any android 10 and above devices? They may have mac address randomization enabled by default. As its name implies, it changes the mac address of your device for privacy reasons.

could be the culprit.

Yes. my phone is android 10, but when I look at the DHCP, I still can see my phone connected.
The mac address never change.

Looks like it also appear in older androids as well. Android 5/6 and onward would use a random address to try to connect but will always end up with the same mac address later. I wonder if this could be causing the temporary mac address that pops up.

https://www.androidpolice.com/2018/03/08/android-p-feature-spotlight-per-network-mac-address-randomization-added-experimental-feature/

I've check the developer settings on my phone, I don't see that setting.
and this doesn't explain why it doesn't happen on TPLink router.

Most probably just random MAC address

Or someone has your password and was accessing it

Did you use same ssid and password on your tplink?

SSID is the same on both router, pw is different.
both pw are extremely complicated.

Ya so basically someone had your old password lmao

Same happen when i using stock router from TM, keep see LED flashing
Then try log in wow keep on got unknown device connected
Even just restart, those unknown device still get connected
After that just buy own router, problem solve

Yes is many year ago when newly apply unifi

Old TM stock router like Dlink router got the TM admin account to access.
So whoever can hack or connect to the network will be able to access the router web panel.

It's not a stock router, if it is a stock router, I won't be surprise this thing happen.
I changed the pw multiple times, and it still happens last time.

Different DHCP implementation on the TPLink router?

You can't do a DHCP request until you get connected to the network so the device doing it already has the access password to your wifi.