If you do that as 

system qq[program "$filename" &];

[download]

It won't matter if the filename contains spaces or not. That's a simple programming problem and hardly worthy of description as "security issue".

As for "injection attacks", I assume that you mean if the source of all or part of the command supplied to the system command is an untrusted external source, then care must be taken. I fail too see how the start command is any more or less of a security risk to invoking an untrusted command directly?

If you get data from untrusted sources, don't you have to be just as careful invoking that data as a command directly as you do invoking it indirectly via a command shell?

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^4: Asynchronous Program Spawning by BrowserUk
in thread Asynchronous Program Spawning by awohld

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