kaspersky 2021 anti-banner is causing issue with jupyterlab, everything is fine if I turn off anti-banner or using Kaspersky 2020. Jupyterlab seems to be not able to connect with python kernel (something with _xsrf as you can see in the screenshot, I guess kaspersky anti-banner modified the traffic/cookie somehow), it will be a potentially big issue as Jupyterlab is widely adapted in scientific community to run python. My system: Win10 x64 2004 KIS 2021 MR1 patch a Python 3.8.5 jupyterlab 2.1.5 Way to reproduce in a clean VM: Install KIS2021 and enable anti-banner Download https://repo.anaconda.com/miniconda/Miniconda3-latest-Windows-x86_64.exe and install Miniconda (tick the option to add conda to PATH) Open command line and type “conda install jupyterlab” and then type “jupyter lab” to open jupyter notebook create a new notebook and connect to python3 kernel, the HTTP403 _xsrf error will occur unless you disable anti-banner before doing step 4 and 5