Sill lets an iPhone or iPad see and control a Mac, so a flaw in it matters. If you find one, please report it privately.

Email support@getsill.app. Say what you found, how to reproduce it, and which versions of Sill for Mac and of the iPhone and iPad app you tried (Sill for Mac's is at the foot of its Settings › General). Please don't open a public issue or pull request for it, and give a fix time to ship before you publish anything. You can also use "Report a vulnerability" on this repository's Security tab.

Fixes ship in the newest release: Sill for Mac from getsill.app, whose update check tells everyone who has it, and the newest iPhone and iPad app.

• The connection on the Mac's own networks, over a USB cable and with Direct Wireless Connection: what Sill for Mac accepts, and what a device can make it do.
• Remote Access's connection, and pairing, at home and away: the QR code, the typed code, sill://pair links, a USB cable's automatic pairing, Require pairing, and the paired devices and keys Sill for Mac keeps in the keychain.
• What another app on the Mac can make Sill for Mac do by starting it, or a copy of it, with arguments and an environment of its own: it then runs with Sill's Screen Recording and Accessibility permissions.
• The update check, which asks GitHub's releases feed about once a day and downloads nothing.
• The website, getsill.app.

Known, and by design: with Require pairing off (Settings › Devices), any device on the Mac's own networks, one nearby while Direct Wireless Connection is on, and any app on the Mac itself connect without pairing, still encrypted. An iPhone or iPad that connects that way takes whatever key answers when its row is tapped, so another Mac on the network that takes the Mac's name could answer that tap; its automatic reconnect goes back only to the key it connected to, and a paired device checks the Mac's key every time. With Show the pairing window to screen sharing on (Settings › encrypted; only a paired device can turn Direct Wireless Connection on or off from its settings panel. With Show the pairing window to screen sharing on (Settings › Devices, off by default), Screen Sharing and other remote desktop apps show the pairing window, so anyone who can see the Mac's screen remotely can read its code. SillHost, the command-line host for development, keeps a plain home door, with no pairing and no encryption, unless it runs with --pairing. Sill for Mac 0.3.1 and earlier had no pairing and no encryption at home: update to the newest release.

The development builds made from source, SillHost and the bare SillMenuBar binary that swift build makes, take test settings that change who gets in and what pairing needs (SILL_TEST_… variables, and the bare binary's -Sill…After arguments and -requirePairing). Sill for Mac takes none of them, whatever its folder is called and however it is started (a renamed copy, a link to its executable): it knows itself by its code signature and its bundle. Sill for Mac 0.4.0 to 0.5.1, and the nightly builds before the next release, knew themselves by their folder's name and take them from a renamed copy or a link: update to the newest release.