the best thing you can do is just keep your computer updated.

The technical details of the vulnerability follow.

Bash supports exporting not just shell variables, but also shell
functions to other bash instances, via the process environment to
(indirect) child processes. Current bash versions use an environment
variable named by the function name, and a function definition
starting with “() {” in the variable value to propagate function
definitions through the environment. The vulnerability occurs because
bash does not stop after processing the function definition; it
continues to parse and execute shell commands following the function
definition. For example, an environment variable setting of

VAR=() { ignored; }; /bin/id

will execute /bin/id when the environment is imported into the bash
process. (The process is in a slightly undefined state at this point.
The PATH variable may not have been set up yet, and bash could crash
after executing /bin/id, but the damage has already happened at this
point.)

The fact that an environment variable with an arbitrary name can be
used as a carrier for a malicious function definition containing
trailing commands makes this vulnerability particularly severe; it
enables network-based exploitation.