Is there any way to override HTML's target="_blank" behavior as an end user?

Is there any way, in any browser, with or without an extension, to override the target="_blank" behavior?

That I am aware of, there is no browser anywhere that will allow you to open a link with a target="_blank" attribute in the same window.

Is anyone aware of any way to override this attribute for end users?

If the page has jquery you can inject the following:

$('a[target="_blank"]').removeAttr('target');

Firefox does allow you to override it:

Users who want to change this behavior need to type in about:config in a tab in the Firefox web browser. This should open the Firefox configuration. First time users need to accept a disclaimer. They then need to filter for the term browser.link.open_newwindow. The default value of that entry is 3 which opens links that would normally open in a new window in a new tab.

To force Firefox to open links (no matter if they have been designed to open in a new tab or window) in the same tab one would need to change the value to [1] which will open all links that would normally open in a new window in the same tab. Changing the value to [2] would open new windows in a new window (duh).

Value of 1: Opens links that would normally open in a new tab or new window in the current tab or window
Value of 2: Open links that would normally open in a new window, in a new window
Value of 3: Open links that would normally open in a new window in a new tab in the current window (default)

You can do this if your browser supports user scripts (such as Chrome or Firefox via a plugin).

Then you can write a user script to override the behaviour for the site/page you are interested in.