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Understanding XSS Attacks ...

Posted: Wed Jan 25, 2012 9:38 pm
by pepe_lepew1962
Hello:

I am really trying to understand XSS attacks and can't seem to wrap my head around it, I would rather seem like a fool than program like one with holes in it. My problem is understanding how an attack occurs. Let's say Mary logs into the system and creates a record in the table via an html form. I have php filters and validation for the data before it actually goes into mysql table. My question is how does John attack my website? Or more important, how does he actually change files? If he were to have a log in and gains access because it doesn't take much to register, how? Is it a matter of the filter being bad and his XSS scipt is in a record and when someone open/views that record (field) the script is launched? I have read lots on how the javascript, for example, is placed in the url or form fields but nothing explains whether the information is saved and launched via the record stored in the database.

Re: Understanding XSS Attacks ...

Posted: Thu Jan 26, 2012 5:05 am
by social_experiment

Re: Understanding XSS Attacks ...

Posted: Thu Jan 26, 2012 10:25 am
by php3ch0
Imagine that someone entered this into their firstname

Code: Select all

<script>alert('Hello'); </script>
if you then displayed the firestname on the website it would be able to run the script (possibly from even an external source)

Re: Understanding XSS Attacks ...

Posted: Thu Jan 26, 2012 10:40 am
by pepe_lepew1962
Ok, so I am understanding it correctly that the attack is actually thru the record/field and my protection is with filters and sanitizing the information BEFORE it goes into the table and htmlcharacters output???

Re: Understanding XSS Attacks ...

Posted: Thu Jan 26, 2012 1:06 pm
by php3ch0
The other thing to consider is SQLInjection someone inserts sql into your script to modify the database. More information can be found here http://www.unixwiz.net/techtips/sql-injection.html