Avast Online Security add-on in Firefox prevents pages loading properly

I’ve noticed recently that certain web pages are not completely loaded, making some well-known sites unusable with Firefox. For example, using the TfL Journey Planner at tfl.gov.uk, the recommended fastest route is not displayed at all. By a process of elimination, I established that it was the Avast Online Security add-on that was causing this.

I’m using Firefox 50.1.0 under Windows 10 Home N version 1607 (both up to date)
Avast Free program version 12.3.2280, engine and definitions version 170110-1 (also up to date)

The Firefox add-on is Avast Online Security 12.0.88 but I note that the version on my Chrome browser is 12.0.163 (and doesn’t cause the problems I have with Firefox). How do I update Avast Online Security for Firefox? Isn’t it part of Avast Free?

I don’t believe the two extensions are bound to have the same version/build number - I too have 12.0.88 on my Firefox installation.

What do you believe is missing I have loaded the page and I have some black empty space at the top, but the rest appears to be OK.

What are the from and to locations and I will try to replicate your query ?

Thanks David. Virtually any journey will do.

I’ve just done Acton Town to Temple (Underground stations in both cases). You should get, below the JOURNEY RESULTS heading and the start and finish locations, “Fastest by public transport” with times and details of the journey followed by “Cycling and other options”. I only get the times and details if Avast Online Security is disabled. If it’s enabled, there is just a blank space between the “Fastest …” and “Cycling …” headings.

Well I have given it a try with AOS add-on disabled and restarted Firefox 50.1.0.

And I have lots of gaps, even with the AOS add-on disabled so I’m unsure what is going on. I have my firefox buttoned up with NoScript, RequestPolicy add-ons and Cookie monster. I even allowed all of the scripts, 3rd party sites and cookies to give the site full access and still it has gaps.

So for the moment you have a better display of the site than I can achieve. I’m at a loss as to what is going on with that site, I don’t believe it is very intuitive.

I tried disabling lots of preferences, essentially trying to allowing only Tube, but it didn’t allow me to kill walking or cycling to restrict it further, but it wouldn’t allow that. It pretty much wanted me to cycle, it must have thought I was Boris.