An angry user on the official DIVX forums noted that his/her browser had been hijacked to force search results to Bing. 
Its more than a simple issue of changing the default homepage, DIVX went to the trouble of installing extensions for Chrome and FireFox, (Safari users simply have to change their homepage back.
In the case the forum thread gets deleted, here’s the copy and pasted de-install instructions from the company representative, Krista.

Hi everyone, we have a few separate threads going with discussions about Conduit and offers in DivX installer. We wanted to respond to all of them all, so we posted a note DivX offers
We’ve gotten a few questions from users through our web tickets about how to do this on Safari and Chrome on Mac so I’m adding those directions here for anyone else who comes across this post. 

To revert the settings in Chrome on Mac: 
  1. Click the ‘hot dog’ button (formerly the wrench icon) and go to “Settings”
  2. In Settings, go to the “On Startup” section; select “Open a specific page or set of pages”. Click on “Set Pages” and select an alternate or add a new page that you prefer to use instead of the Conduit option.
  3. In Settings, go to the “Appearance” section; check the box for “Show Home Button”. Click the “Change” link, select “Open This Page” and write in the page you want to use as your home page.
  4. In Settings, go to the “Search” section. Click “Manage Search engines…” Add or select a new default search engine, then remove the Conduit option.
  5. In your search box go to chrome://extensions and remove the Conduit Search tool and DivX Browser Bar tool.
  6. Close and reopen the browser to see the changes take effect.

To revert the settings in Safari: 
  1. Go to Safari and select “Preferences”
  2. Under the General section go to “Home Page”
  3. Change the home page from the Conduit search option to something else (e.g.www.google.com)
In Firefox on Mac, you can change your Home Page by following these steps: 
  1. In the “Firefox” menu, select “Preferences”
  2. Under the General section, find the Home Page area.
  3. Remove the current Home Page option and write in a new one, for example “http://www.google.com”
  4. Close and Reopen the browser to see the changes take effect.

To change the New Tab page in Firefox on Mac: 
  1. Open a new tab
  2. Click the “Restore” button in the bottom left corner of the page.
  3. Close and Reopen the browser to see the changes take effect.

To change the search engine for the search bar: 
  1. Click on the menu next to the magnifying glass icon in the upper-right corner of the browser window.
  2. Select “Manage Search Engines”
  3. Select a new search engine as your default, for example Google.
  4. Remove the DivX Browser Bar/Conduit option from the list

To change the 404 error page: 
  1. Go to the Firefox folder: open Finder and navigate to Applications and right click on firefox.app
  2. Select MacOS, and delete the MACSearchTakeOver.js file
  3. Go to the folder Users/USERNAME/Library/Application Support/Firefox/Profiles/CHOOSEActiveProfile. Note, USERNAME = your username. CHOOSEActiveProfile will be a unique name, for example “6y5m281v.default”
  4. Delete the file called abstraction.js

Source: forums.divx.com/divx/topics/bing_search_page_appears_when_opening_a_new_tab_window_on_firefox_macos

Interestingly, as someone with an affinity for codecs, its been quite some time since I’ve thought about DIVX. Last night, I was updating my Flip4Mac codecs so I could use Camtasia (and checking my 3VIX codecs) but since the advent of .H264 and AAC, its hard to really think of using any other end-user codecs besides .H264 (and WebM for FireFox users).

DIVX is so irrelevant today that popular Sorenson Squeeze doesn’t even bother to output to it. It doesn’t surprise me that they’ve fallen to RealMedia’s RealPlayer shovelware tactics.