JavaScript: Difference between revisions
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*[[wikipedia:Arbitrary_code_execution|Arbitrary code execution]] and [[wikipedia:Code_injection|code injection]]. Typically caused by <code>[https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval eval]</code> (part of the ECMAScript spec), but there are Web APIs (such as <code>[https://developer.mozilla.org/en-US/docs/Web/API/Window/setTimeout setTimeout]</code> and <code>[https://developer.mozilla.org/en-US/docs/Web/API/Window/setInterval setInterval]</code>) that can be misused as well. | *[[wikipedia:Arbitrary_code_execution|Arbitrary code execution]] and [[wikipedia:Code_injection|code injection]]. Typically caused by <code>[https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval eval]</code> (part of the ECMAScript spec), but there are Web APIs (such as <code>[https://developer.mozilla.org/en-US/docs/Web/API/Window/setTimeout setTimeout]</code> and <code>[https://developer.mozilla.org/en-US/docs/Web/API/Window/setInterval setInterval]</code>) that can be misused as well. | ||
*Remote code execution. This is used by hackers and crackers to build [[wikipedia:Botnet|bot-nets]] for [[wikipedia:Ddos#Distributed_DoS|DDoS]] or [[wikipedia:Cryptocurrency|crypto]]-mining, but it's mostly used for [[spyware]] since it can hide more easily. | *Remote code execution. This is used by hackers and crackers to build [[wikipedia:Botnet|bot-nets]] for [[wikipedia:Ddos#Distributed_DoS|DDoS]] or [[wikipedia:Cryptocurrency|crypto]]-mining, but it's mostly used for [[spyware]] since it can hide more easily. | ||
Browser-engine developers (such as [[Google]] and [[Mozilla]]) not only feel compelled, but are economically incentivized to optimize JS to its limits.{{Citation needed}} This leads to complex code-bases that are harder to verify for correctness. Browser vendors mitigate this via [[wikipedia:Sandbox_(computer_security)|sandboxing]]. Unfortunately, since modern browsers compile JS to native CPU code (see [[wikipedia:Just-in-time_compilation|JIT]]) to improve performance, this introduces a higher risk of sandbox-escape | Browser-engine developers (such as [[Google]] and [[Mozilla]]) not only feel compelled, but are economically incentivized to optimize JS to its limits.{{Citation needed}} This leads to complex code-bases that are harder to verify for correctness. Browser vendors mitigate this via [[wikipedia:Sandbox_(computer_security)|sandboxing]]. Unfortunately, since modern browsers compile JS to native CPU code (see [[wikipedia:Just-in-time_compilation|JIT]]) to improve performance, this introduces a higher risk of sandbox-escape.<ref>{{Cite web |last=Norman |first=Johnathan |date=2021-08-04 |title=Super Duper Secure Mode |url=https://microsoftedge.github.io/edgevr/posts/Super-Duper-Secure-Mode/ |url-status=live |archive-url=https://web.archive.org/web/20260218110912/https://microsoftedge.github.io/edgevr/posts/Super-Duper-Secure-Mode |archive-date=2026-02-18 |access-date=2026-03-19 |website=Microsoft Browser Vulnerability Research}}</ref> | ||
JS not only makes pages "dynamic", the language itself is very dynamic, which is hard to optimize by engines. To put into perspective how much JS can slow down rendering, someone bench-marked a bloated pure-HTML page and a "simple" [[wikipedia:React_(software)|React]] app, the bloated HTML had faster [https://developer.mozilla.org/en-US/docs/Glossary/First_meaningful_paint FMP].<ref>{{Cite web |last=Leatherman |first=Zach |date=2019-09-06 |title=Which has a better First Meaningful Paint time? |url=https://twitter.com/zachleat/status/1169998370041208832 |url-status=live |archive-url=https://web.archive.org/web/20240529104252/https://x.com/zachleat/status/1169998370041208832 |archive-date=2024-05-29 |access-date=2024-05-29 |website=Twitter/X}}</ref> | JS not only makes pages "dynamic", the language itself is very dynamic, which is hard to optimize by engines. To put into perspective how much JS can slow down rendering, someone bench-marked a bloated pure-HTML page and a "simple" [[wikipedia:React_(software)|React]] app, the bloated HTML had faster [https://developer.mozilla.org/en-US/docs/Glossary/First_meaningful_paint FMP].<ref>{{Cite web |last=Leatherman |first=Zach |date=2019-09-06 |title=Which has a better First Meaningful Paint time? |url=https://twitter.com/zachleat/status/1169998370041208832 |url-status=live |archive-url=https://web.archive.org/web/20240529104252/https://x.com/zachleat/status/1169998370041208832 |archive-date=2024-05-29 |access-date=2024-05-29 |website=Twitter/X}}</ref> | ||