Geth v1.8.15 is a small patch release on top of v1.8.14 (Khazad-dûm) to fix a few issues discovered post-release and to implement a few missing features to make mining "complete":

• Fix a data race that could lead to corruption if multiple PoW solutions are found concurrently within the same mining cycle, but for different work tasks (#17489).
• Fix a data corruption if a PoW solution is found to an older block within a single mining cycle (#17490).
• Fix the timestamp and difficulty for recommitted transaction sets at the same block height (17547).
• Fix CPU mining for embedded in-process go-ethereum instances (#17492).
• Extend the logs to differentiate between reorged-but-included and reorged-and-excluded blocks (#17494).
• Extend ethash to accept stale results for past mining tasks and track them as potential uncles (#17506).
• Make uncle tracking stateless to permit correct inclusion even in the face or large-ish reorgs (#17540).
• Support skipping PoW verification for remote miner submissions via --miner.noverify (#17506).
• Support hard capping the gas limit of mined blocks via --miner.gaslimit (#17546).

Note, --miner.gastarget and --miner.gaslimit defaults to 8M starting from this release. If you require different values, make sure you set them explicitly. Puppeth was also extended to support both configs.

For a full rundown of the changes please consult the Geth 1.8.15 release milestone.

Geth binaries and mobile libraries are available on the Geth download page.

A quick recap of the miner features introduced in v1.8.14:

• Track multiple miner work packages concurrently, permitting miners to start working on an empty block and replace it in the background with a full one, reducing mining delay by 200+ ms on mainnet (#15853, #17323).
• Insert uncles instantly into active work packages instead of waiting till the next block (#17320, #17469).
• Recommit active mining work every 3 seconds, maximizing block fullness and miner fees (#17413).
• Configurable recommit interval with dynamic adjustment in case of system overload (#17444).
• Support miner push notifications for new work packages via HTTP POST requests (#17347).
• Support priority mining for local transactions, specifiable via --txpool.locals (#17472).
• Log block fullness and expected fees for current miner work package (#17416, #17426).
• Remote mining will use memory mapped ethash DAGs instead of caches (#17405).
• Clean up miner CLI flags and deprecate old ones (#17402).

Note, there are two minor breaking changes wrt mining: 1) remote mining requires the --mine flag from now on and will not automatically start on a eth_getWork request; 2) --mine will not start a CPU miner, you need to explicitly specify --miner.threads=N in addition.