Yes, but it might last until next Halloween or beyond. Candy bars are high in sugar and low in moisture, both of which help to prevent microbial growth. Pure chocolate can last for two years or more without presenting any acute health risks, but it’s likely to change in texture and become less appetizing after about 12 months. Given enough time, some bars could even become so dry and hard as to be inedible (or at least a danger to your teeth). More serious, nondental health risks are very unlikely, however.
The white spots or haze that sometimes appear on old chocolate bars is known among chocolatiers as “blooming,” and it’s harmless to your health. Blooming isn’t mold, as some candy-lovers might think, but rather a splotch of fat or sugar that has risen to the surface. Fat blooming is caused by fluctuations in temperature, while sugar blooming is caused by condensation and changes in humidity. To avoid the whitening—which affects a candy's appearance and its texture—store your candy bars in a cool, dry place away from the sun.