diff --git a/modules/sharethroughBidAdapter.js b/modules/sharethroughBidAdapter.js
index a7a64e0bda3..7fe41b2b7ae 100644
--- a/modules/sharethroughBidAdapter.js
+++ b/modules/sharethroughBidAdapter.js
@@ -1,10 +1,17 @@
 import { registerBidder } from '../src/adapters/bidderFactory';
 
-const VERSION = '3.0.1';
+const VERSION = '3.1.0';
 const BIDDER_CODE = 'sharethrough';
 const STR_ENDPOINT = document.location.protocol + '//btlr.sharethrough.com/WYu2BXv1/v1';
 const DEFAULT_SIZE = [1, 1];
 
+// this allows stubbing of utility function that is used internally by the sharethrough adapter
+export const sharethroughInternal = {
+  b64EncodeUnicode,
+  handleIframe,
+  isLockedInFrame
+};
+
 export const sharethroughAdapterSpec = {
   code: BIDDER_CODE,
 
@@ -37,10 +44,10 @@ export const sharethroughAdapterSpec = {
       // Data that does not need to go to the server,
       // but we need as part of interpretResponse()
       const strData = {
-        stayInIframe: bidRequest.params.iframe,
+        skipIframeBusting: bidRequest.params.iframe,
         iframeSize: bidRequest.params.iframeSize,
         sizes: bidRequest.sizes
-      }
+      };
 
       return {
         method: 'GET',
@@ -59,7 +66,7 @@ export const sharethroughAdapterSpec = {
     const creative = body.creatives[0];
     let size = DEFAULT_SIZE;
     if (req.strData.iframeSize || req.strData.sizes.length) {
-      size = req.strData.iframeSize != undefined
+      size = req.strData.iframeSize
         ? req.strData.iframeSize
         : getLargestSize(req.strData.sizes);
     }
@@ -102,7 +109,7 @@ export const sharethroughAdapterSpec = {
 
   // Empty implementation for prebid core to be able to find it
   onSetTargeting: (bid) => {}
-}
+};
 
 function getLargestSize(sizes) {
   function area(size) {
@@ -125,35 +132,72 @@ function generateAd(body, req) {
     <div data-str-native-key="${req.data.placement_key}" data-stx-response-name="${strRespId}">
     </div>
     <script>var ${strRespId} = "${b64EncodeUnicode(JSON.stringify(body))}"</script>
-  `
+  `;
 
-  if (req.strData.stayInIframe) {
+  if (req.strData.skipIframeBusting) {
     // Don't break out of iframe
-    adMarkup = adMarkup + `<script src="//native.sharethrough.com/assets/sfp.js"></script>`
+    adMarkup = adMarkup + `<script src="//native.sharethrough.com/assets/sfp.js"></script>`;
   } else {
-    // Break out of iframe
+    // Add logic to the markup that detects whether or not in top level document is accessible
+    // this logic will deploy sfp.js and/or iframe buster script(s) as appropriate
     adMarkup = adMarkup + `
-      <script src="//native.sharethrough.com/assets/sfp-set-targeting.js"></script>
       <script>
-        (function() {
-          if (!(window.STR && window.STR.Tag) && !(window.top.STR && window.top.STR.Tag)) {
-            var sfp_js = document.createElement('script');
-            sfp_js.src = "//native.sharethrough.com/assets/sfp.js";
-            sfp_js.type = 'text/javascript';
-            sfp_js.charset = 'utf-8';
-            try {
-                window.top.document.getElementsByTagName('body')[0].appendChild(sfp_js);
-            } catch (e) {
-              console.log(e);
-            }
-          }
-        })()
-    </script>`
+        (${sharethroughInternal.isLockedInFrame.toString()})()
+      </script>
+      <script>
+        (${sharethroughInternal.handleIframe.toString()})()
+      </script>`;
   }
 
   return adMarkup;
 }
 
+function handleIframe () {
+  // only load iframe buster JS if we can access the top level document
+  // if we are 'locked in' to this frame then no point trying to bust out: we may as well render in the frame instead
+  var iframeBusterLoaded = false;
+  if (!window.lockedInFrame) {
+    var sfpIframeBusterJs = document.createElement('script');
+    sfpIframeBusterJs.src = '//native.sharethrough.com/assets/sfp-set-targeting.js';
+    sfpIframeBusterJs.type = 'text/javascript';
+    try {
+      window.document.getElementsByTagName('body')[0].appendChild(sfpIframeBusterJs);
+      iframeBusterLoaded = true;
+    } catch (e) {
+      console.error(e);
+    }
+  }
+
+  var clientJsLoaded = (!iframeBusterLoaded) ? !!(window.STR && window.STR.Tag) : !!(window.top.STR && window.top.STR.Tag);
+  if (!clientJsLoaded) {
+    var sfpJs = document.createElement('script');
+    sfpJs.src = '//native.sharethrough.com/assets/sfp.js';
+    sfpJs.type = 'text/javascript';
+
+    // only add sfp js to window.top if iframe busting successfully loaded; otherwise, add to iframe
+    try {
+      if (iframeBusterLoaded) {
+        window.top.document.getElementsByTagName('body')[0].appendChild(sfpJs);
+      } else {
+        window.document.getElementsByTagName('body')[0].appendChild(sfpJs);
+      }
+    } catch (e) {
+      console.error(e);
+    }
+  }
+}
+
+// determines if we are capable of busting out of the iframe we are in
+// if we catch a DOMException when trying to access top-level document, it means we're stuck in the frame we're in
+function isLockedInFrame () {
+  window.lockedInFrame = false;
+  try {
+    window.lockedInFrame = !window.top.document;
+  } catch (e) {
+    window.lockedInFrame = (e instanceof DOMException);
+  }
+}
+
 // See https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding#The_Unicode_Problem
 function b64EncodeUnicode(str) {
   return btoa(
diff --git a/test/spec/modules/sharethroughBidAdapter_spec.js b/test/spec/modules/sharethroughBidAdapter_spec.js
index d8feac3d0a2..afa5f44959c 100644
--- a/test/spec/modules/sharethroughBidAdapter_spec.js
+++ b/test/spec/modules/sharethroughBidAdapter_spec.js
@@ -1,5 +1,5 @@
 import { expect } from 'chai';
-import { sharethroughAdapterSpec } from 'modules/sharethroughBidAdapter';
+import { sharethroughAdapterSpec, sharethroughInternal } from 'modules/sharethroughBidAdapter';
 import { newBidder } from 'src/adapters/bidderFactory';
 
 const spec = newBidder(sharethroughAdapterSpec).getSpec();
@@ -46,7 +46,7 @@ const prebidRequests = [
       placement_key: 'pKey'
     },
     strData: {
-      stayInIframe: false,
+      skipIframeBusting: false,
       sizes: []
     }
   },
@@ -58,7 +58,7 @@ const prebidRequests = [
       placement_key: 'pKey'
     },
     strData: {
-      stayInIframe: true,
+      skipIframeBusting: true,
       sizes: [[300, 250], [300, 300], [250, 250], [600, 50]]
     }
   },
@@ -70,7 +70,7 @@ const prebidRequests = [
       placement_key: 'pKey'
     },
     strData: {
-      stayInIframe: true,
+      skipIframeBusting: true,
       iframeSize: [500, 500],
       sizes: [[300, 250], [300, 300], [250, 250], [600, 50]]
     }
@@ -83,7 +83,7 @@ const prebidRequests = [
       placement_key: 'pKey'
     },
     strData: {
-      stayInIframe: false,
+      skipIframeBusting: false,
       sizes: [[0, 0]]
     }
   },
@@ -95,7 +95,7 @@ const prebidRequests = [
       placement_key: 'pKey'
     },
     strData: {
-      stayInIframe: false,
+      skipIframeBusting: false,
       sizes: [[300, 250], [300, 300], [250, 250], [600, 50]]
     }
   },
@@ -120,27 +120,71 @@ const bidderResponse = {
   header: { get: (header) => header }
 };
 
-// Mirrors the one in modules/sharethroughBidAdapter.js as the function is unexported
-const b64EncodeUnicode = (str) => {
-  return btoa(
-    encodeURIComponent(str).replace(/%([0-9A-F]{2})/g,
-      function toSolidBytes(match, p1) {
-        return String.fromCharCode('0x' + p1);
-      }));
-}
-
 const setUserAgent = (str) => {
   window.navigator['__defineGetter__']('userAgent', function () {
     return str;
   });
-}
+};
+
+describe('sharethrough internal spec', function () {
+  let windowSpy, windowTopSpy;
+
+  beforeEach(function() {
+    windowSpy = sinon.spy(window.document, 'getElementsByTagName');
+    windowTopSpy = sinon.spy(window.top.document, 'getElementsByTagName');
+  });
+
+  afterEach(function() {
+    windowSpy.restore();
+    windowTopSpy.restore();
+    window.STR = undefined;
+    window.top.STR = undefined;
+  });
+
+  describe('we cannot access top level document', function () {
+    beforeEach(function() {
+      window.lockedInFrame = true;
+    });
+
+    afterEach(function() {
+      window.lockedInFrame = false;
+    });
+
+    it('appends sfp.js to the safeframe', function () {
+      sharethroughInternal.handleIframe();
+      expect(windowSpy.calledOnce).to.be.true;
+    });
+
+    it('does not append anything if sfp.js is already loaded in the safeframe', function () {
+      window.STR = { Tag: true };
+      sharethroughInternal.handleIframe();
+      expect(windowSpy.notCalled).to.be.true;
+      expect(windowTopSpy.notCalled).to.be.true;
+    });
+  });
+
+  describe('we are able to bust out of the iframe', function () {
+    it('appends sfp.js to window.top', function () {
+      sharethroughInternal.handleIframe();
+      expect(windowSpy.calledOnce).to.be.true;
+      expect(windowTopSpy.calledOnce).to.be.true;
+    });
+
+    it('only appends sfp-set-targeting.js if sfp.js is already loaded on the page', function () {
+      window.top.STR = { Tag: true };
+      sharethroughInternal.handleIframe();
+      expect(windowSpy.calledOnce).to.be.true;
+      expect(windowTopSpy.notCalled).to.be.true;
+    });
+  });
+});
 
 describe('sharethrough adapter spec', function () {
   describe('.code', function () {
     it('should return a bidder code of sharethrough', function () {
       expect(spec.code).to.eql('sharethrough');
     });
-  })
+  });
 
   describe('.isBidRequestValid', function () {
     it('should return false if req has no pkey', function () {
@@ -176,7 +220,7 @@ describe('sharethrough adapter spec', function () {
       expect(builtBidRequests[0].url).to.eq(
         'http://btlr.sharethrough.com/WYu2BXv1/v1');
       expect(builtBidRequests[1].url).to.eq(
-        'http://btlr.sharethrough.com/WYu2BXv1/v1')
+        'http://btlr.sharethrough.com/WYu2BXv1/v1');
       expect(builtBidRequests[0].method).to.eq('GET');
     });
 
@@ -230,7 +274,7 @@ describe('sharethrough adapter spec', function () {
       const builtBidRequests = spec.buildRequests(bidRequests);
       expect(builtBidRequests[0]).to.deep.include({
         strData: {
-          stayInIframe: undefined,
+          skipIframeBusting: undefined,
           iframeSize: undefined,
           sizes: [[600, 300]]
         }
@@ -253,7 +297,7 @@ describe('sharethrough adapter spec', function () {
         });
     });
 
-    it('returns a correctly parsed out response with largest size when strData.stayInIframe is true', function () {
+    it('returns a correctly parsed out response with largest size when strData.skipIframeBusting is true', function () {
       expect(spec.interpretResponse(bidderResponse, prebidRequests[1])[0]).to.include(
         {
           width: 300,
@@ -267,7 +311,7 @@ describe('sharethrough adapter spec', function () {
         });
     });
 
-    it('returns a correctly parsed out response with explicitly defined size when strData.stayInIframe is true and strData.iframeSize is provided', function () {
+    it('returns a correctly parsed out response with explicitly defined size when strData.skipIframeBusting is true and strData.iframeSize is provided', function () {
       expect(spec.interpretResponse(bidderResponse, prebidRequests[2])[0]).to.include(
         {
           width: 500,
@@ -281,7 +325,7 @@ describe('sharethrough adapter spec', function () {
         });
     });
 
-    it('returns a correctly parsed out response with explicitly defined size when strData.stayInIframe is false and strData.sizes contains [0, 0] only', function () {
+    it('returns a correctly parsed out response with explicitly defined size when strData.skipIframeBusting is false and strData.sizes contains [0, 0] only', function () {
       expect(spec.interpretResponse(bidderResponse, prebidRequests[3])[0]).to.include(
         {
           width: 0,
@@ -295,7 +339,7 @@ describe('sharethrough adapter spec', function () {
         });
     });
 
-    it('returns a correctly parsed out response with explicitly defined size when strData.stayInIframe is false and strData.sizes contains multiple sizes', function () {
+    it('returns a correctly parsed out response with explicitly defined size when strData.skipIframeBusting is false and strData.sizes contains multiple sizes', function () {
       expect(spec.interpretResponse(bidderResponse, prebidRequests[4])[0]).to.include(
         {
           width: 300,
@@ -324,29 +368,27 @@ describe('sharethrough adapter spec', function () {
       expect(spec.interpretResponse(bidResponse, prebidRequests[0])).to.be.an('array').that.is.empty;
     });
 
-    it('correctly generates ad markup', function () {
+    it('correctly generates ad markup when skipIframeBusting is false', function () {
       const adMarkup = spec.interpretResponse(bidderResponse, prebidRequests[0])[0].ad;
       let resp = null;
 
       expect(() => btoa(JSON.stringify(bidderResponse))).to.throw();
-      expect(() => resp = b64EncodeUnicode(JSON.stringify(bidderResponse))).not.to.throw();
+      expect(() => resp = sharethroughInternal.b64EncodeUnicode(JSON.stringify(bidderResponse))).not.to.throw();
       expect(adMarkup).to.match(
         /data-str-native-key="pKey" data-stx-response-name=\"str_response_bidId\"/);
       expect(!!adMarkup.indexOf(resp)).to.eql(true);
-      expect(adMarkup).to.match(
-        /<script src="\/\/native.sharethrough.com\/assets\/sfp-set-targeting.js"><\/script>/);
-      expect(adMarkup).to.match(
-        /sfp_js.src = "\/\/native.sharethrough.com\/assets\/sfp.js";/);
-      expect(adMarkup).to.match(
-        /window.top.document.getElementsByTagName\('body'\)\[0\].appendChild\(sfp_js\);/)
+
+      // insert functionality to autodetect whether or not in safeframe, and handle JS insertion
+      expect(adMarkup).to.match(/isLockedInFrame/);
+      expect(adMarkup).to.match(/handleIframe/);
     });
 
-    it('correctly generates ad markup for staying in iframe', function () {
+    it('correctly generates ad markup when skipIframeBusting is true', function () {
       const adMarkup = spec.interpretResponse(bidderResponse, prebidRequests[1])[0].ad;
       let resp = null;
 
       expect(() => btoa(JSON.stringify(bidderResponse))).to.throw();
-      expect(() => resp = b64EncodeUnicode(JSON.stringify(bidderResponse))).not.to.throw();
+      expect(() => resp = sharethroughInternal.b64EncodeUnicode(JSON.stringify(bidderResponse))).not.to.throw();
       expect(adMarkup).to.match(
         /data-str-native-key="pKey" data-stx-response-name=\"str_response_bidId\"/);
       expect(!!adMarkup.indexOf(resp)).to.eql(true);