The good news is that the macOS Big Sur 11.3.1 update, available from Apple (opens in new tab) today, will fix the bugs in question, but you should follow along to make sure that your laptop is updated immediately as Apple itself acknowledges that the threat may have been actively exploited already (via MacRumors).
macOS Big Sur reviewBest MacBook in 2021: Which Apple laptop is best?The best Apple deals for May 2021
There are two aspects to the bug, both affecting WebKit. The first is a memory corruption issue and the second an integer overflow. According to Apple, either one could lead to arbitrary code execution if triggered by malicious content delivered via the web. Again, the macOS 11.3.1 update will eliminate both bugs, so just verify that your system is up-to-date.
How to update macOS Big Sur right now
Click the Apple icon in the upper-left cornerSelect System PreferencesClick on Software UpdateSelect Upgrade Now
That’s it, the update will download itself and follow the on-screen instructions to complete installation.