This Server has a plug-in installed which provides you the gift grab drop. Server is for the next few month online 51.89.165.30:27015
Thanks to Leeson.
guide: https://v1.steam.hlxgame.cc/sharedfiles/filedetails/?id=2296578058

Check my recent Counter Strike: Source Screenshots.
https://v1.steam.hlxgame.cc/id/davethewaves/screenshots/
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Waiting for this achievement to work since a long time.
I like to achieve this achievement in the way it meant to.

Name of the achievement was changed in june 2017 from:
Valve Gift Grab 2011 - CS:S
to
Gift Grab

However, you still can´t obtain this achievement for Counter-Strike: Source

We can maybe get the attention for the developers to fix the achievement if we stick together in this group.

Feel free to add your friends to this group via the blue "invite friends" button in the upper right hand side.

suggestions to this group are welcome.

Group Name: Counter-Strike: Source Gift Grab Achievement
Abbreviation: CSS_GiftGrab
Group link: https://v1.steam.hlxgame.cc/groups/CSS_GiftGrab/

You can get some informations on the following link:
(the information about the gift grab is obtainable in any wintner event is missleading - in CSS case for sure)

Counter Strike Wiki[counterstrike.wikia.com]