OWASP disagrees: See https://cheatsheetseries.owasp.org/cheatsheets/Nodejs_Securi..., listing `eval()` first in its small list of examples of "JavaScript functions that are dangerous and should only be used where necessary or unavoidable". I'm unaware of any such uses, myself. I can't think of any scenario where I couldn't get what I wanted by using some combination of `vm`, the `Function` constructor, and a safe wrapper around `JSON.parse()` to do anything I might have considered doing unsafely with `eval()`. Yes, `eval()` is a blatant red flag and definitely should be avoided.
While there are valid use cases for eval they are so rare that it should be disabled by default and strongly discouraged as a pattern. Only in very rare cases is eval the right choice and even then it will be fraught with risk.
The parent didn't say "there's no legitimate uses of eval", they said "using eval should make people pay more attention." A red flag is a warning. An alert. Not a signal saying "this is 100% no doubt malicious code."
Yes, it's a red flag. Yes, there's legitimate uses. Yes, you should always interrogate evals more closely. All these are true
Not that long, browsers implemented JSON.parse() back in 2009. JSON was only invented back in 2001 and took a while to become popular. It was a very short window more than a decade ago when eval made sense here.
Eval for json also lead to other security issues like XSSI.
And why do we not anymore make use of it, but instead implemented separate JSON loading functionality in JavaScript? Can you think of any reasons beyond performance?
I actually gave it some thought. I had written the actual reason first, but I realized that the person I was responding to must know this, yet keeps arguing in that eval is just fine.
I would say they are arguing that in bad faith, so I wanted to enter a dialogue where they are either forced to agree, or more likely, not respond at all.
OWASP disagrees: See https://cheatsheetseries.owasp.org/cheatsheets/Nodejs_Securi..., listing `eval()` first in its small list of examples of "JavaScript functions that are dangerous and should only be used where necessary or unavoidable". I'm unaware of any such uses, myself. I can't think of any scenario where I couldn't get what I wanted by using some combination of `vm`, the `Function` constructor, and a safe wrapper around `JSON.parse()` to do anything I might have considered doing unsafely with `eval()`. Yes, `eval()` is a blatant red flag and definitely should be avoided.
While there are valid use cases for eval they are so rare that it should be disabled by default and strongly discouraged as a pattern. Only in very rare cases is eval the right choice and even then it will be fraught with risk.
The parent didn't say "there's no legitimate uses of eval", they said "using eval should make people pay more attention." A red flag is a warning. An alert. Not a signal saying "this is 100% no doubt malicious code."
Yes, it's a red flag. Yes, there's legitimate uses. Yes, you should always interrogate evals more closely. All these are true
When is an eval not at least a security "code smell"?
It really is. There are very few proper use-cases for eval.
For a long time the standard way of loading JSON was using eval.
Not that long, browsers implemented JSON.parse() back in 2009. JSON was only invented back in 2001 and took a while to become popular. It was a very short window more than a decade ago when eval made sense here.
Eval for json also lead to other security issues like XSSI.
Problem is, it took until around 2016 for IE6 to be fully dead, so people continued to justify these hacks for a long time. Horrifying times.
For IE7 support, yes... https://caniuse.com/mdn-javascript_builtins_json_parse
And why do we not anymore make use of it, but instead implemented separate JSON loading functionality in JavaScript? Can you think of any reasons beyond performance?
I'd be surprised if there is a performance benefit of processing json with eval(). Browsers optimize the heck out of JSON.
You are arguing against the opposite of what the comment you answered to said.
Why did you opt in for such a comment while a straight forward response without belittling tone would have achieved the same?
I actually gave it some thought. I had written the actual reason first, but I realized that the person I was responding to must know this, yet keeps arguing in that eval is just fine.
I would say they are arguing that in bad faith, so I wanted to enter a dialogue where they are either forced to agree, or more likely, not respond at all.