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64 lines
2.5 KiB
Plaintext
64 lines
2.5 KiB
Plaintext
CLP-01-001 DOMXSS in Clipperz Bookmarklet via benign HTML Injection (Medium)
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Insecure concatenation of HTML strings in the Clipperz bookmarklet core
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lead to possibilities for an attacker, to turn a harmless injection on a
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victim website into an XSS as soon as a user activates the bookmarklet.
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The bookmarklet contains injectable code that allows arbitrary
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JavaScript execution from a harmless injection as shown below:
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PoC:
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(run Clipperz Bookmarklet on this website)
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<body>
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<form action=''>
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<input name='username' type='text'>
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<input name='</textarea><img src=x onerror=alert(domain)>' type='password'>
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</form>
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Affected HTML:
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<textarea style="border:2px solid #333366; font-family:sans-serif;
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font-size:8pt; color:#336; width:240px; height:135px; padding:4px;
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background-color:white; margin:0px 10px;"
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id="bookmarklet_textarea">{"page": {"title": ""},
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"form": {"attributes": {"action": "http://0x0/Test/",
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"method": null},
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"inputs": [{"type": "text",
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"name": "username",
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"value": "root"},
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{"type": "password",
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"name": "</textarea><img onerror="alert(domain)" src="x">",
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"value": "k4n0n3!?"}]},
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"version": "0.2.3"}</div>
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Affected Code:
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innerHTML+="<textarea id=\"bookmarklet_textarea\" style=\"border:2px
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solid #333366; font-family:sans-serif; font-size:8pt; color:#336;
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width:240px; height:135px; padding:4px; background-color:white;
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margin:0px 10px;\">"+sj(someParameters)+"</textarea>";}
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...
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sj=function(o){var
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objtype=typeof(o);if(objtype=="number"||objtype=="boolean"){return
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o+"";}else if(o===null){return"null";} if(objtype=="string"){return
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rs(o);} var
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me=arguments.callee;if(objtype!="function"&&typeof(o.length)=="number"){var
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res=[];for(var i=0;i<o.length;i++){var
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val=me(o[i]);if(typeof(val)!="string"){val="undefined";} res.push(val);}
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return"["+res.join(",\n")+"]";}
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...
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rs=function(o){return("\""+o.replace(/([\"\\])/g,"\\$1")+"\"").replace(/[\f]/g,"\\f").replace(/[\b]/g,"\\b").replace(/[\n]/g,"\\n").replace(/[\t]/g,"\\t").replace(/[\r]/g,"\\r");}
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Any form of HTML, even content of HTML element attributes must be
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considered an attack vector. Currently, Clipperz does a good job in
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terms of encoding HTML element value attributes, yet other attribute
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types are not escaped, encoded or filtered at all. This lead to the
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identification of this and other bugs, specifically CLP-01-014 and
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CLP-01-015.
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It needs to be made sure, that any form of user controlled data is being
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processed safely before displaying the resulting data. HTML special
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characters need to be encoded to their respected entity representation
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before displaying them.
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