What was the vulnerability in v0.3.4 that allowed an attacker to steal coins? Reference: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2010-5141

What was the specific exploit in the Tx script evaluation process?
Explanation by Mike Hearn:
https://bitcointalk.org/index.php?topic=152470.msg1620493#msg1620493


  When Bitcoin was first released, it contained two completely fatal
  bugs that made the entire system worthless. Fortunately, they were
  found and fixed before Bitcoin  actually had any serious value.
  
  The first bug was that scripts were concatenated before being run
  instead of just using a shared stack. This meant that anyone could
  write a scriptSig that always evaluated to true and claim anyone elses
  coins. Fixed here in v0.3.2:
  
  https://github.com/bitcoin/bitcoin/commit/73aa262647ff9948eaf95e83236ec323347e95d0


...


  Needless to say, if somebody when this version was first released
  actually wrote such a scriptSig and stole some coins, that would have
  caused a chain split between old and new versions. Nobody did because,
  why bother? I'm not even sure Mt Gox existed back then, iirc that came
  some months later. Many script opcodes were disabled around this time
  (which is also a hard-forking change).