540490 - Minefield takes all available CPU when Adblock Plus is enabled

Status: RESOLVED INVALID

(Web Compatibility :: Site Reports, defect)

Description

[Michael]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.3a1pre) Gecko/20100118 Minefield/3.7a1pre
Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.3a1pre) Gecko/20100118 Minefield/3.7a1pre

At http://usa.visa.com/merchants/new_acceptance/how_it_works.html

If I go to that page with adblock plus enabled, CPU usage slowly climbs until the browser is taking all available CPU.  Browser responsiveness (such as scrolling) goes to near 0.  If the page is whitelisted, the problem does not occur.  All browser functions are affected.

Reproducible: Always

Steps to Reproduce:
1. Run adblock plus (may require a certain rule to be active, but I'm not sure - it may be that a certain script is being prevented from running)
2. browser CPU usage climbs by about 10% per second.  On OS X, it was reported at 140% before I killed it.
3. Whitelist page.  Problem does not occur.
Actual Results:  
Browser takes all available CPU

Expected Results:  
A poorly behaved site, or a site that has had some javascript blocked, should not cause the failure of the browser.  The site should be given some maximum amount of CPU time, or other measures should be taken to isolate the site from the rest of the browser.

Comment 1

[Ria Klaassen (not reading all bugmail)]

Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.3a1pre) Gecko/20100118 Minefield/3.7a1pre

Indeed one core goes very high.

Comment 2

[Ria Klaassen (not reading all bugmail)]

It seems to be caused by a filter. No hang without filters so far.

Comment 3

[Ria Klaassen (not reading all bugmail)]

|http://www.google-analytics.com/* seems to be the problem here for me.

Comment 4

[Brian Carpenter [:geeknik]]

Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.3a1pre) Gecko/20100118 Firefox/3.7a1pre

I'm not seeing any increased CPU usage on that URL.

Comment 5

[Wladimir Palant]

Could be bug 508542 again - however, "|http://www.google-analytics.com/*" isn't an exponential filter, are you sure it is causing this?

Comment 6

[Wladimir Palant]

Forget what I said above, I reproduced the issue. This is an ill-behaved site indeed, if Google Analytics fails to load (because of Adblock Plus or otherwise) it goes into an endless loop. JavaScript Deobfuscator shows this function getting almost a thousand calls per second:

    function () {
        try {
            if (!a) {
                a = _gat._getTracker("UA-8460445-1");
            }
        } catch (b) {
            console.log(b);
            VISA.GoogleAnalytics.includeAnalyticsJS();
            setTimeout(VISA.GoogleAnalytics.getPageTracker, 100);
        }
    }

This function happens to be VISA.GoogleAnalytics.getPageTracker from http://usa.visa.com/js/visa.js - so if the analytics script didn't load it tries again as a "fallback" behavior. There is a delay here, so one such loop shouldn't be too bad. I guess that this function gets called a number of times on page load which creates a few dozen such loops. Together they cause this CPU load.

Either way, extension compatibility is the wrong component. This is either tech evangelism (if we want Visa to fix their site) or Core / JavaScript (if we want the "slow script" warning to consider scripts creating too many events).

Comment 7

[Wladimir Palant]

Note that this isn't an issue for most Adblock Plus users - most filter subscriptions no longer block the main Google Analytics script, this breaks too many websites. Instead they block the tracking image that this script creates. I looked through the list of recommendation - it seems that only RuAdList is still doing this (however, it isn't recommended in any released version yet).

Comment 8

[Michael]

On the other hand, I create my own custom filters, and *do* block google-analytics completely, which may be why I hit it.  It hasn't caused a problem on any other website though.

What is the filter to block the tracking image?

Comment 9

[Wladimir Palant]

EasyPrivacy uses "/__utm.gif" to block it.

Comment 10

[Michael]

This page takes 100% of CPU on minefield, even if Adblock Plus is disabled, resulting in a hang.  Not sure if this is the same problem or not:

http://www.aigaviation.com/aviationsalvage/salvagedetail.aspx?faano=N106US

Comment 11

[Ria Klaassen (not reading all bugmail)]

The thumbnails are not really thumbnails but resized 2.592px × 1.944px images. This explain also the scrolling problems. Firefox has to calculate.

Comment 12

[Karl Dubost💡 :karlcow]

The initial page doesn't exist anymore.
http://usa.visa.com/merchants/become-a-merchant/how-a-visa-transaction-works.jsp