What do we call a software update that fixes bugs and vulnerabilities?

A software update that specifically addresses bugs and vulnerabilities is referred to as a patch. Patches are designed to improve the stability, performance, and security of software applications by correcting flaws and weaknesses that could potentially be exploited by attackers. This process is crucial in maintaining the integrity of systems and protecting sensitive data from unauthorized access.

In contrast, an update is a broader term that encompasses any changes made to software, which could include new features, improvements, and bug fixes, not solely focused on security issues. An upgrade usually refers to a significant enhancement or a new version of the software that may include substantial changes or added functionality. A release, on the other hand, typically signifies the distribution of a complete version of software to the public or specific users, often including multiple features and updates.

Thus, the term patch is specifically suited to describe the targeted updates that address particular issues in software, making it the correct answer in this context.