Stochastic Activation Pruning (SAP) (Dhillon et al., 2018) is a defense to
adversarial examples that was attacked and found to be broken by the
"Obfuscated Gradients" paper (Athalye et al., 2018). We discover a flaw in the
re-implementation that artificially weakens SAP. When SAP is applied properly,
the proposed attack is not effective. However, we show that a new use of the
BPDA attack technique can still reduce the accuracy of SAP to 0.1%.