I didn't see any response to this, so here's an explanation.
"mset" is the System Settings program. Among other things, it allows you to change the DS profile name. A buffer overflow error in mset (starting in 4.1 I think?) allowed for
arbitrary code execution due to a stack smash. Since the DS profile name could be set by any DS game (including flash carts), it was fairly popular as one of the first widespread 3DS exploits. The mset exploit was fixed in 7.0.
Regarding people still using RXtools: Whining about it won't get you anywhere.
- Constantly bashing people for using RXtools is on the level of "stop liking what I don't like". What would you think if you were bashed for playing 3DS games instead of, say, mobile apps?
- If RXtools is working for someone, great. If they encounter an issue with one of the tools (e.g. eMMC backup) let them know that there's newer entry points and CFWs available that might fix the issue.
- Newer is not necessarily better. In the case of A9LH vs. menuhax and mset, sure; but what about other things like Windows 7 vs. Windows 10? (I personally prefer OSes that don't shove worthless apps in my face every five minutes.) [Bonus option: Newer 3DS firmware that patches exploits versus older 3DS firmware that still has exploits.]