v4.26, produces no output, errors in the log

I just upgraded pgAdmin from 4.24 to 4.26 (python wheel install) and almost
all result tabs are now blank.
Neither Query nor Explain produce any result. I cleared all chrome cache
(cookies, session/local storage), restarted the backend with no success.

I rolled back to 4.24 and everything works as before.

Version: 4.26
Copyright (C) 2013 - 2020, The pgAdmin Development Team
Python Version: 3.8.2 (default, Jul 16 2020, 14:00:26) [GCC 9.3.0]
Flask Version: 1.0.2
Application Mode: Desktop
Current User: pgadmin4(at)pgadmin(dot)org
OS: "20.04.1 LTS (Focal Fossa)"

The log is a repetition of the same error (see below)

===============================================
2020-10-08 12:25:39,125: ERROR flask.app: 400 Bad Request: The CSRF
session token is missing.
Traceback (most recent call last):
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 256, in protect
validate_csrf(self._get_csrf_token())
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 94, in validate_csrf
raise ValidationError('The CSRF session token is missing.')
wtforms.validators.ValidationError: The CSRF session token is missing.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask/app.py",
line 1811, in full_dispatch_request
rv = self.preprocess_request()
File "/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask/app.py",
line 2087, in preprocess_request
rv = func()
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 224, in csrf_protect
self.protect()
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 259, in protect
self._error_response(e.args[0])
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 302, in _error_response
raise CSRFError(reason)
flask_wtf.csrf.CSRFError: 400 Bad Request: The CSRF session token is
missing.
2020-10-08 13:01:37,714: ERROR flask.app: 400 Bad Request: The CSRF
session token is missing.
Traceback (most recent call last):
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 256, in protect
validate_csrf(self._get_csrf_token())
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 94, in validate_csrf
raise ValidationError('The CSRF session token is missing.')
wtforms.validators.ValidationError: The CSRF session token is missing.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask/app.py",
line 1811, in full_dispatch_request
rv = self.preprocess_request()
File "/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask/app.py",
line 2087, in preprocess_request
rv = func()
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 224, in csrf_protect
self.protect()
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 259, in protect
self._error_response(e.args[0])
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 302, in _error_response
raise CSRFError(reason)
flask_wtf.csrf.CSRFError: 400 Bad Request: The CSRF session token is
missing.
2020-10-08 13:01:42,712: ERROR flask.app: 400 Bad Request: The CSRF
session token is missing.
Traceback (most recent call last):
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 256, in protect
validate_csrf(self._get_csrf_token())
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 94, in validate_csrf
raise ValidationError('The CSRF session token is missing.')
wtforms.validators.ValidationError: The CSRF session token is missing.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask/app.py",
line 1811, in full_dispatch_request
rv = self.preprocess_request()
File "/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask/app.py",
line 2087, in preprocess_request
rv = func()
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 224, in csrf_protect
self.protect()
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 259, in protect
self._error_response(e.args[0])
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 302, in _error_response
raise CSRFError(reason)
flask_wtf.csrf.CSRFError: 400 Bad Request: The CSRF session token is
missing.
2020-10-08 13:01:44,035: ERROR flask.app: 400 Bad Request: The CSRF
session token is missing.
Traceback (most recent call last):
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 256, in protect
validate_csrf(self._get_csrf_token())
File
"/home/user/opt/pgadmin4/lib/python3.8/site-packages/flask_wtf/csrf.py",
line 94, in validate_csrf
raise ValidationError('The CSRF session token is missing.')
wtforms.validators.ValidationError: The CSRF session token is missing.

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