Eike Rathke authored Jan 05, 2019 and Kevin J. McCarthy committed Jan 05, 2019

time_t return of time() may be signed 32-bit and in that case
probably will roll over in the year 2038 and yield a negative
value; signedness was propagated in the XOR operation to the
'value' and then 'v' variables. The 'v % 62' operation then would
had resulted in a negative value and LETTER[v%62] would had
accessed an arbitrary data location.

The same could had happened if the static long 'value' variable
after a very long run time contained a sufficiently large value to
which the time^pid value added resulted in a wrap / roll-over to a
negative value.

Using unsigned long types for 'value' and 'v' and casting time_t
to unsigned long cures all this.