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Reasons never to allow HTML
by
10 Aug 2004
This was written in response to various queries regarding the use of HTML, most recently in this thread. ----------------- In general, one is probably fine allowing bbcodes, although I do not know if bbcodes like IMG and URL are safe. (See below.) While vB provides the capability to allow HTML, one should never use it. It opens your board to attack. Use bbcodes. If you need to emulate an HTML tag, write a new bbcode. The problem with allowing the injection of HTML is a complicated one. There is no 100% safe method to allow HTML and feel secure. Some of the issues and interactions are: 1. The obviously dangerous tags like SCRIPT and APPLET are not the only danger. Any injection of a URL can be dangerous. Any tag that allows for a URL (e.g., a, img, frame, ...) can be used for cross-site scripting and cookie stealing, which can allow someone to hack into your board. 2. Hackers can use various tricks that would result in a tag getting through the filter imposed by the PHP checker. Possible examples: a) <sc\0ript> becomes <script> b) <scr<embed>ipt> becomes <embed> or <script> 3. Then there is the issue of malicious tag attributes and events such as onclick and onmouseup. -------- Potentially dangerous tags that accept URL's: A, APPLET, AREA, BASE, BGSOUND, BODY, EMBED, FORM, FRAME, IFRAME, ILAYER, IMG, ISINDEX, INPUT, LAYER, LINK, OBJECT, SCRIPT, SOUND, TABLE, TD, TH, TR The following members like this post: CarpCharacin
Last edited by CarCdr; 10 Aug 2004 at 13:31.. |
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#2
10 Aug 2004, 13:11
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I'll move this over to modifications hints and tips - I think we need a rename of that forum
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Dean Clatworthy - Web Developer/Designer No members have liked this post.
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#3
11 Aug 2004, 00:19
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Handy Hints 4 Board Admins?
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Natcher00 ... is the Admin @ MobileForces.org - Official Community for a cult Vehicle based FPS - the only place for support! ... also he's Penfold to Dark_Wizard's Danger Mouse in development of vBWar http://www.mobileforces.org/sig.jpg {DaniWeb: Learn HOW-TO mod_rewrite your vB board} No members have liked this post.
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#4
11 Aug 2004, 01:52
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good hints
HTML is magic. No members have liked this post.
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#5
17 Aug 2005, 23:41
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Or you can just censor certain html tags and be a little safer:
:ermm: No members have liked this post.
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#6
17 Aug 2005, 23:44
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Originally Posted by Gutspiller
Censor is really easy to get around
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Looking for ImpEx?
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#7
25 Aug 2005, 00:54
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i have an even better reason /;
do not alow <img /> tags!! <HTML> <BODY> <IMG SRC="./bsod.gif" width="9999999"height="9999999" /> </BODY> </HTML> INSTANT DOOM!! muahahahahahaha (it chrashes the page 
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#8
25 Aug 2005, 07:23
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Originally Posted by Gutspiller
there are still so many more possibilities to use vicious javascript and code
__________________
My Site:Animation Talk My Hacks:Vb3 Affiliate Version 1:vB Affiliates v.2:vB Journal 1.0.0:Quick Attachment Approval System: UnBannable Ips:Text Message on PM:Selected Files Not Closed:New Thread/Post Image Verification for Guests: vB Stocks 1.0.0 This means this hack won an award. No members have liked this post.
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#9
25 Aug 2005, 22:14
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and theres always my instant doom img tag
the downside is, you gota upload your own pic /; No members have liked this post.
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#10
28 Sep 2005, 05:17
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And when enabling HTML only for Admins, would that be safe, beside the risk that someone gets Admin access?
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#11
30 Jan 2013, 15:44
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Do they have to register an account and write something in the HTML-enabled section in order to exploit security vulnerabilities, or is it enough to just enable HTML in the first place in order to open up the forum for vulnerabilities?
__________________
“Human beings are animals: very unusual animals, to be sure, but nevertheless animals. In origin, we are not fallen angels, but apes arisen.” — Michael H. Hart UADisplay for the nerds among us who care about browser wars!
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#12
30 Jan 2013, 16:10
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Originally Posted by EliasAlucard
The risk is someone using the HTML on your forum. So whatever usergroup has the ability, is where the risk lies.
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#13
30 Jan 2013, 16:16
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Originally Posted by Digital Jedi
Do they have to post with special HTML tags or is it enough that someone posts something like <sup> in order to enable HTML to become a vulnerability risk?
__________________
“Human beings are animals: very unusual animals, to be sure, but nevertheless animals. In origin, we are not fallen angels, but apes arisen.” — Michael H. Hart UADisplay for the nerds among us who care about browser wars!
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#14
30 Jan 2013, 18:04
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Originally Posted by EliasAlucard
The danger doesn't come from the HTML just existing in a post. The danger comes from the person posting using raw HTML code.
Whatever HTML code he puts in a post, becomes that on the forum. If he posts the code that makes a table, it becomes a table in his post. If he posts the raw HTML code for embedding a YouTube video, it becomes an embedded YouTube video in his posts. So the danger comes from the person, and what he's choosing to post. If he wants to post malicious code, he has fee access to do so. That's why BBCode is more secure. BBCode only turns into the HTML you decided it will turn into. NOTE: Don't confuse this with the [HTML][/HTML] BBCode tags. This has nothing to do with what they're talking about above. This just displays code in such a way that it stays formatted. No matter what anyone puts here, it will just display text with the spacing preserved and color coding added.
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#15
30 Jan 2013, 22:31
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Wow a 9 year old thread revived?
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