#Javascript, 14 bytes

Golfed

setInterval(0)

Registers an empty interval handler with a default delay, discarding the resulting timer id (making it impossible to cancel).

I've used a non-default interval, to create several million timers, to illustrate the leak, as using a default interval eats CPU like mad.

Javascript, 14 bytes

Golfed

setInterval(0)

Registers an empty interval handler with a default delay, discarding the resulting timer id (making it impossible to cancel).

I've used a non-default interval, to create several million timers, to illustrate the leak, as using a default interval eats CPU like mad.