On October 3, 2013, Adobe announced that their network and some of their servers had been breached. Their investigation continues, and the full scope and impact of the breach has yet to be determined.

However, we do know the following:

• The intruders obtained Adobe customer data, including customer names, encrypted credit or debit card numbers, expiration dates, and other information relating to customer orders. According to Adobe, “At this time, we do not believe the attackers removed decrypted credit or debit card numbers from our systems.” Adobe reset the passwords for all affected user accounts, and has been sending out alerts to those users. If you have never purchased software from Adobe directly, you should be safe. If you receive an alert from Adobe, follow their instructions to change your password.
• The intruders also obtained source code for at least one product: Acrobat/Reader. Reader is already a popular target for malware perpetrators, and having access to the source code can only make things easier for them. Stay tuned for a fresh new crop of Reader security issues.

Ars Technica has additional details, as does the SANS ISC Diary.

Update 2013Nov02: Ars Technica explains exactly what Adobe did wrong and why we should all be worried about it. Adobe now says that as many as 38 million users were affected by the breach.

Update 2014Oct10: Duo Security reviews the fallout from this breach, and warns of the dangers of password hints.