In plain words
Think of macros like a set of instructions that can automatically do tasks for you in a document, like a recipe for your computer. But just like how a bad recipe can make you sick, a bad macro can harm your computer.
What's broken
The bug is in how Microsoft Excel¹ handles a type of file called SYLK², which can contain macros³. An attacker could make a malicious SYLK file that, when opened in Excel, would run the attacker's code on the computer. This is called remote code execution⁴, or RCE⁴.
How it actually works
Here's how it works: an attacker sends you a SYLK file with a malicious macro³. When you open the file in Excel, the macro³ runs, which can then execute the attacker's code⁴. This happens because Excel doesn't properly check the macro³ for malicious instructions before running it. The term RCE⁴ refers to the ability of an attacker to run any code they want on your computer, which is very dangerous. The term macro³ refers to a set of instructions that can be executed by a program, in this case Excel. The term SYLK² refers to a type of file that can contain these instructions.
Proof of concept
There is a public proof-of-concept⁵, or PoC⁵, that demonstrates this flaw is real and can be exploited. A PoC⁵ is like a demonstration that shows a flaw is not just theoretical but can actually be used to attack a computer. The existence of a public PoC⁵ makes this flaw more urgent because it shows that attackers can use it. The term PoC⁵ refers to a demonstration of how a flaw can be exploited.
Is it real
It's not clear from the source if this flaw is being actively exploited in the wild. However, the fact that it's a 0day⁶ flaw means that there is no official patch yet, making it particularly dangerous. The term 0day⁶ refers to a flaw that is publicly known but does not yet have a patch.
What to do
To protect yourself, you should be cautious when opening files from unknown sources, especially SYLK files, and consider turning off macros³ in Excel until a patch is available. The term patch refers to a fix for a bug in a program.
Terms
- ¹ Microsoft Excel¹
- , A software application used for creating and editing spreadsheets
- ² SYLK²
- , A type of file that can contain instructions for a program
- ³ macro³
- , A set of instructions that can be executed by a program
- ⁴ RCE⁴
- , The ability of an attacker to run any code they want on your computer
- ⁵ PoC⁵
- , A demonstration of how a flaw can be exploited
- ⁶ 0day⁶
- , A flaw that is publicly known but does not yet have a patch