You must verify that all 'important' values are 'reasonable' when they come up to your .cgi application.
For instance, the price for an article that the visitor is going to buy should not be stored on the client side. Or at least, your .cgi application should not use it. Because a smart(?) client could change it and buy your product for 1 cent. Or for -100 dollars. (Hup! Will you send the money with the product? :-)

Some basic rules of thumb:
- Almost anything provided by the visitor may be stored in the visitors browser.
- Anything provided by your site cannot be trusted if it's been down to the client. You must verify and check it again. (Like using the price from your database, not from the client browser.)
- If you want to give the visitor some sort of safety, like using a password or such, it will become even more complicated.

Best regards
Biker

In reply to Re: Modiying values in html form by Biker
in thread Modiying values in html form by kiat

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.