From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.9) Gecko/20020528

Description of problem:
When using a entry from /etc/mailcap, Mozilla apparently only uses the command
name, and ignores the rest of the command line.

Version-Release number of selected component (if applicable):0.9.9-13


How reproducible:
Always

Steps to Reproduce:
1.Add an entry "image/x-xwindowdump; xwud -in %s" in /etc/mailcap
  assuming no other configuration for this content-type.
2.Point mozilla to a file with an .xwd suffix.


Actual Results:  Mozilla first asks if it should use xwud to display this file.
 If accepted, another window is quickly flashed, and then gone.

Expected Results:  A new xwud window with the contents of the xwd file.

Additional info:

Apparently, Mozilla invokes "xwud <file>" omitting the "-in" in the mailcap entry.

I hesitated a bit before categorising this as a security bug.  It could be a
security issue if mailcap consists an entry like "gv -safer %s", where the
mozilla behaviour would effectively remove the -safer flag.  In the end I
decided to call it a security issue, reasoning it is easy to downgrade it if
inappropriate.