History of Clear the Cache

Clear the Cache is a Season of the Splicer triumph: open Corrupted Chests with Corrupted Key Codes in Expunge.

How to complete

1. Obtain Corrupted Key Codes. They are a rare drop from enemies killed in both PvE and PvP; they appear as blue items and stack to five, so do not dismantle them from your postmaster by accident. TheGamer suggests farming the Thrall Room in the Shattered Throne dungeon, which spawns an endless stream of easy-to-kill Shadow Thrall.
2. Run a corrupted version of an Expunge mission. When the boss dies a Corrupted Conflux Chest spawns.
3. Use a key code on the chest. Opening one chest with a key code completes the objective as described in-game.

The chests can contain Lightkin armor, Override weapons and Umbral Engrams, and the first three corrupted chests opened each week are improved by Splicer Gauntlet upgrades (TheGamer).

Seal

Shacknews lists this among the Season of the Splicer triumphs but states it is not one of the ten triumphs required for the Splicer seal.

Notes

The exact number of chests the objective needs is not given in the sources I opened. Drop rates are described as very low and may have changed since Season 14.