Information

Full output of /ess version:

Server version: 1.8.8-R0.1-SNAPSHOT git-Spigot-21fe707-e1ebe52 (MC: 1.8.8)
29.08 18:32:43 [Server] INFO EssentialsX version: 2.18.1.0
29.08 18:32:43 [Server] INFO PlaceholderAPI version: 2.10.6
29.08 18:32:43 [Server] INFO GroupManager version: Pre2.14.1.3 FINAL (Phoenix)
29.08 18:32:43 [Server] INFO Vault version: 1.5.6-b49
29.08 18:32:43 [Server] INFO Citizens version: 2.0.16-SNAPSHOT (build 1267)
29.08 18:32:43 [Server] INFO EssentialsXChat version: 2.18.1.0
29.08 18:32:43 [Server] INFO EssentialsXSpawn version: 2.18.1.0
29.08 18:32:43 [Server] INFO ChestShop version: 3.8.12

Details

Description
/ci ** clears everyone's inventory.

Steps to reproduce
Use the command /clear **, /clearinventory **, or /ci **

Expected behavior
/ci ** is supposed to clear only my Inventory and Armor Slots.

I believe just /ci clears all your inventory, doing ** to target everyone seems intentional.

Wow I really messed up this command, fix soon.

The command is /ci <player> **, so it seems like it's doing what it should

Yes, but the problem is that /ci ** should do like all commands and target myself (ex. /god, /fly, etc.) unless a player is specified.
/ci * clears all inventories, not /ci **

And thank you @JRoy !

I feel like that would cause more confusion than anything, since ** is already inconsistent enough with what it does

Well, that's the way it has been for years now and I've grown accustom to it.
I do get your point though, especially when commands like /eco set ** 0 would clear EVERYONE'S balance on the server, one might think /ci ** clears everyone's inventory (offline and online).

Yet commands like /kit <kit> * and /kit <kit> ** do absolutely nothing - really strange.

This has been fixed as of f898405 - you can download the latest version of EssentialsX from the website.