1063836 - image alt text should be empty if channel is cancelled with NS_ERROR_TRACKING_URI

Status: RESOLVED WONTFIX

(Core :: DOM: Security, defect)

Description

[[:mmc] Monica Chew (no longer reading bugmail)]

It's arguable whether this is a good idea or not. STR

0) Enable tracking protection
1) Visit theverge.com
2) See "tracking_pixel_5345_tracker" in the top left. This is a 1x1 pixel being blocked but the alt text is shown.

I'm not familiar with broken image handling from http://www.w3.org/html/wg/drafts/html/master/embedded-content.html but I am guessing this might be working as intended.

However, in this particular case, the UA is blocking the image from loading even though it might be available. Would it make sense for the image loader to nullify the alt-text if the channel is cancelled with NS_ERROR_TRACKING_URI? This could happen here:

http://mxr.mozilla.org/mozilla-central/source/content/base/src/nsImageLoadingContent.cpp#175

Comment 1

[[:mmc] Monica Chew (no longer reading bugmail)]

Seth, what do you think?

Comment 2

[Seth Fowler [:seth] [:s2h]]

Not clearing the needinfo because I don't have time to look at the spec right now, but unless there's something preventing us from doing this spec-wise I agree with your proposal. The current behavior does seem like a poor user experience.

Comment 3

[Seth Fowler [:seth] [:s2h]]

So after thinking about this a little more, I think I'm going to change my view here. I don't think we should do this.

The reason is that any alt attributes that will cause problems when images don't load due to tracking protection will also cause problems for users that rely on text-to-speech software, are on a poor connection, or are using a text-only browser. The spec explicitly states that content authors should use an empty alt attribute for such images here:

http://www.w3.org/html/wg/drafts/html/master/embedded-content.html#an-image-not-intended-for-the-user

I think we are doing users a favor by making the circumstances in which this kind of bad alt text appears more frequent. This will encourage content authors to fix their sites, which will make the web a friendlier and more inclusive place.

I'm definitely open to further discussion on this, though. I'm assuming, for example, that this doesn't cause enough widespread bustage that people won't want to surf with tracking protection on. (It didn't seem that way in my testing but I only tried a few sites.)

Comment 4

[[:mmc] Monica Chew (no longer reading bugmail)]

Thanks for weighing in, Seth. I'm going to mark this as WONTFIX until we have more dogfood feedback, since we have only 2 complaints so far.