diff --git a/DeDRM_plugin/topazextract.py b/DeDRM_plugin/topazextract.py
index 97d75a7..4f2c057 100644
--- a/DeDRM_plugin/topazextract.py
+++ b/DeDRM_plugin/topazextract.py
@@ -358,7 +358,16 @@ class TopazBook:
                         destdir =  os.path.join(outdir,"page")
                     if name == b'glyphs':
                         destdir =  os.path.join(outdir,"glyphs")
+                    # The record name is read verbatim from the (untrusted) book
+                    # file, so strip any directory components to stop a crafted
+                    # name (e.g. "../../foo") from writing outside of destdir.
+                    fname = os.path.basename(fname)
                     outputFile = os.path.join(destdir,fname)
+                    # Defense in depth: never let the resolved path escape destdir.
+                    real_out = os.path.abspath(outputFile)
+                    real_dir = os.path.abspath(destdir)
+                    if not (real_out == real_dir or real_out.startswith(real_dir + os.sep)):
+                        raise DrmException("Invalid book record name: {0}".format(repr(name)))
                     print(".", end=' ')
                     record = self.getBookPayloadRecord(name,index)
                     if isinstance(record, str):