Firefox Dev Tools showing "blocked requests" to Matomo

When working with Matomo, I notice on some websites that the Firefox console with the network analysis shows that Firefox had blocked the requests to Matomo and a NS_ERROR_FAILURE was happened.
See the screenshot.
However, in the Matomo visitor log I see that the tracking requests arrived and were processed.

I investigated this further.
The Firefox behavior occurs when
a) Matomo is addressed on a subdomain or domain other than that of the website.
b) The web server has set an HTTP header x-xss-protection “1; mode=block”

Unfortunately, I come across variant b) very often, even though Mozilla says that you shouldn’t use this header.


But ultimately, it looks like the request is processed to Matomo, even if Firefox says otherwise.
So I can ignore this message. Hopefully :wink:

Hi @utrautma
It seems that FF sends the request to the Matomo server, but does not accept the server response… That’s why the tracking works well anyway…
In my opinion, you shouldn’t let errors in HTTP or JavaScript console. Try to solve the XSS issue (can’t you use CSP headers instead of X-XSS obsolete header?)

Hello @heurteph-ei ,

thank you for your feedback. I see it the same way as you. However, I have found some websites with this setup and am not responsible for it. But I will give the webmasters appropriate information.
As far as I know, there is no XSS issue there, but rather incorrect use of an old HTTP header

1 Like