Build ID: 2001081205 FizzillaCFM Steps to reproduce: 1) Browse pages at http://planetprint.com/ or try the string concatenation test at chofmann's browser buster. Actual results: The infamous color wheel curson shows up and Mozilla doesn't respond to user input while the script is running. Expected results: Expected JS from the Web to not be able to make the UI unresponsive. At least the stop button should work. Additional information: I suppose doing something about this is difficult. However, in the long term, it would be good if this was fixed. The current situation makes denial of service attacks possible. A rogue script can make Mozilla unresponsive and the user has no choice but to zap the entire process.

Over to JavaScript Engine.

The site http://planetprint.com uses layers, which are non-W3C and not supported by Mozilla/N6. From http://planetprint.com/dhtmllib.js : /****************************************************************************** * dhtmllib.js * * * * Copyright 1999 by Mike Hall. * * Web address: http://www.brainjar.com * * Last update: February 26, 2000. * * * * Provides basic functions for DHTML positioned elements which will work on * * both Netscape Communicator and Internet Explorer browsers (version 4.0 and * * up). * ******************************************************************************/ // Determine browser. var isMinNS4 = (navigator.appName.indexOf("Netscape") >= 0 && parseFloat(navigator.appVersion) >= 4) ? 1 : 0; var isMinIE4 = (document.all) ? 1 : 0; var isMinIE5 = (isMinIE4 && navigator.appVersion.indexOf("5.") >= 0) ? 1 : 0; //----------------------------------------------------------------------------- // Layer visibility. //----------------------------------------------------------------------------- function hideLayer(layer) { if (isMinNS4) layer.visibility = "hide"; if (isMinIE4) layer.style.visibility = "hidden"; } function showLayer(layer) { if (isMinNS4) layer.visibility = "show"; if (isMinIE4) layer.style.visibility = "visible"; } etc. etc. And from http://planetprint.com/js/navbar.js : function navBarCreate() { if (isMinNS4) str += '<layer name="navBar' + this.index + '_filler"></layer>\n' + '<layer name="navBar' + this.index + '_hdrsBase">\n'; etc. etc.

As for the string concatenation issue, that has been filed as: bug 56940 O(n**2) and O(n**3) growth too easy with JS string concat Also see: bug 40391 "JS + on long strings freezes mozilla, horks Win98" bug 64589 "Recursive Javascript/DOM additions crash browser HARD" (this turned out to be due to JS string concatenation) bug 74918 "Appending strings in JavaScript bogs down Mozilla" *** This bug has been marked as a duplicate of 56940 ***

Verified as Duplicate. I have filed Bug 95148 on the layer issue and cc'ed henris@clinet.fi -