2422 WASM, add reason for disabling, fixes #1037 (#1054)

user.js

@@ -1047,8 +1047,14 @@ user_pref("javascript.options.asmjs", false);
    // user_pref("javascript.options.ion", false);
    // user_pref("javascript.options.baselinejit", false);
    // user_pref("javascript.options.jit_trustedprincipals", true); // [FF75+] [HIDDEN PREF]
-/* 2422: disable WebAssembly [FF52+] [SETUP-PERF]
- * [1] https://developer.mozilla.org/docs/WebAssembly ***/
+/* 2422: disable WebAssembly [FF52+]
+ * Vulnerabilities have increasingly been found, including those known and fixed
+ * in native programs years ago [2]. WASM has powerful low-level access, making
+ * certain attacks (brute-force) and vulnerabilities more possible
+ * [STATS] ~0.2% of websites, about half of which are for crytopmining / malvertising [2][3]
+ * [1] https://developer.mozilla.org/docs/WebAssembly
+ * [2] https://spectrum.ieee.org/tech-talk/telecom/security/more-worries-over-the-security-of-web-assembly
+ * [3] https://www.zdnet.com/article/half-of-the-websites-using-webassembly-use-it-for-malicious-purposes ***/
 user_pref("javascript.options.wasm", false);
 /* 2429: enable (limited but sufficient) window.opener protection [FF65+]
  * Makes rel=noopener implicit for target=_blank in anchor and area elements when no rel attribute is set ***/