I think this will expire at the end of the Holiday Sale 2015, i.e. 4/1/2016 PST. Do this as soon as you can.
EDIT: SPOILERS! (if you're trying to solve the ARG yourself)
Get the "hidden" Steam badge, Red Herring, and 100 XP by completing the following steps:
- Open Steam in your web browser: http://store.steampowered.com/
- Log in to your Steam account.
- Turn off Adblock Plus or any other ad blockers.
- Open the store page for Ikaruga: http://store.steampowered.com/app/253750
- Type in the Steam search box: search
- Press Enter
- A text box appears. Type: 1v7531
- Click OK.
- The page will refresh and you'll see your new badge.
If the page doesn't refresh then try again but at Step 7 try typing in the code, don't copy/paste from here.
It seems that some people are having issues with it working on Firefox. Try another browser. Others reporting works in Google Chrome.
Don't forget that increasing your Steam XP increases your booster pack drop rate.
Source: How to get the Red Herring Steam Badge (Holiday Sale 2015 ARG)
Background
Valve is running a hidden mystery game in the form of an ARG (alternate reality game) in conjunction with the Holiday Sale 2015. The clues are in the pages on the comic. Some very smart people in the /r/steamsaledetectives reddit have found and solved all the puzzles.
im lost at step 4