
diff -r 0a42d73e795b -r 4b454a6d1814 handouts/ho01.tex
--- a/handouts/ho01.tex	Fri Jul 15 10:54:09 2016 +0100
+++ b/handouts/ho01.tex	Sun Aug 21 00:37:27 2016 +0100
@@ -220,8 +220,17 @@
 found at \url{http://www.computerbytesman.com/redos/}.}
 Admittedly, this regular expression is carefully chosen to
 exhibit this exponential behaviour, but similar ones occur
-more often than one wants in ``real life''. They are sometimes
-called \emph{evil regular expressions} because they have the
+more often than one wants in ``real life''. For example, on 20
+July 2016 a similar regular expression brought the webpage
+\href{http://stackexchange.com}{Stack Exchange} to its knees:
+
+\begin{center}
+\url{http://stackstatus.net/post/147710624694/outage-postmortem-july-20-2016}
+\end{center}
+
+\noindent
+Such troublesome regular expressions are sometimes called
+\emph{evil regular expressions} because they have the
 potential to make regular expression matching engines to
 topple over, like in Python and Ruby. The problem with evil
 regular expressions is that they can have some serious
@@ -229,8 +238,8 @@
 web-application. The reason is that hackers can look for these
 instances where the matching engine behaves badly and then
 mount a nice DoS-attack against your application. These
-attacks are already have their own name: 
-\emph{Regular Expression Denial of Service Attacks (ReDoS)}.
+attacks are already have their own name: \emph{Regular
+Expression Denial of Service Attacks (ReDoS)}.
 
 It will be instructive to look behind the ``scenes'' to find
 out why Python and Ruby (and others) behave so badly when




