I meant to blog about this when 4.2 was released, but didn’t get around to it. it seems like there’s a bit of confusion about the security of screensaver widgets. also, I figured I should remind everyone that to turn them on you go to hte screensaver KCM. :) quick summary: so long as you use common sense when adding widgets, and take a minute to test them, it should be perfectly safe. and if you’re feeling paranoid, you can just leave them disabled, of course.
the thing about screensaver security is, it’s not really about protecting against malicious code. that’s important too, but it applies to all of plasma. for the screensaver, I have to think about malicious (or simply meddlesome) users. if I leave my screen locked at school when I go to the bathroom, I don’t want to come back to find goatse or files deleted or anything mean like that (and yes, I’ve been in classes where this was a problem).
back in summer I looked over the code of every damn plasmoid in workspace, kdeplasma-addons and playground. what I found surprised me. nearly every plasmoid fell into one of two categories: completely and utterly harmless (like the bouncy ball), or completely inappropriate for the screensaver (like the taskbar and folderview). only a handful were in-betweens: a few launched external programs, which were safely hidden behind the screensaver but still there to be annoying when the screen was unlocked, and a few had actual security issues (like twitter, unless you *want* random strangers posting to your account). not only that, but most of the inappropriate ones were contained in a few categories. those categories have become a little more fuzzy since then, but there are still two or three that could just be banned from the screensaver entirely.
so, it turns out this isn’t so much a security problem as a “keep the inappropriate plasmoids from cluttering the appletbrowser” problem. if you sit and think for a minute about the plasmoids you’ve added to your screensaver, maybe poke at them while it’s locked to see if you can break stuff, you’ll easily see whether your screensaver is safe to leave unattended. the only thing I didn’t find completely obvious was that the battery applet lets me suspend from the screensaver (and personally I consider that a feature).
there are two things I had planned: making it possible to filter out the inappropriate plasmoids from the appletbrowser using categories and some security constraints, and making it possible for the small number of plasmoids in the grey area to ask if they need to act more securely, so that they can be allowed on the screensaver too. unfortunately this got derailed by other things not happening, and now some of the detailed notes are lost, but someday I’ll find time to do it…