Hey all just got this in an e-mail today but already booked my holidays for the year damn, anyway,
Not sure when the Shopback promos finish but the Groupon code expires in 12 hours apparently.
Link for Groupon Shopback here
Editor's notes: OP's title and description were a little confusing, so here are my clarifications.
Deal 1: Increased cashback 40% on Deposits for Hostelworld, up from 15% @ Shopback
Deal 2: Increased cashback 15% for Groupon, up from 7% @ Shopback
Deal 3: Groupon MEGASALE: extra 5%/10%/15% discount expires 29/11/2018. Enter coupon code at Groupon checkout. Stacks with Deal 2. Original deal post
Just note that for the Hostelworld deal, the 40% only applies to the compulsory deposit, which is quite small…