Depends how old, and where.
In series = Safe
Going to ground = Dangerous
Old = High ESR
Newer = Low ESR
If you are replacing a series cap, relatively ( < 10 years) new, you are fine.
If the cap is old, it probably has higher ESR, and that should be taken into account, but in series it's not much of a problem.
The problem is in shunts ( 2nd component in low pass) where loosing a couple of ohms can dump the speaker impedance to 2 Ohms, and cause you to loose amplifier output.