There has been a Observer/Sentry wards bug discovered in Dota 6.70c map which allows you to restock a single ward into two. This major exploit is working on all the previous versions of DotA including the stable 6.69c. It is very simple to reproduce it in a real game with the help of courier and it can be game-breaking at some point. Check the DotA 6.70c bug video & it's guide.
1. Buy an item courier & 5 Ironwood Branches.
2. Summon courier and give all 5 Ironwood branches to it.
3. Now buy Observer/Sentry wards and another Ironwood branch on your hero.
4. <span id="IL_AD1" class="IL_AD">Plant the first Observer/Sentry ward and give the second ward to the courier <span style="font-weight: bold;">(make sure it goes in right last <span id="IL_AD2" class="IL_AD">inventory</span> slot of courier)</span>
5. Drop Ironwood Branch from your hero that you bought in Step#3.
6. Select courier hold [Shift] and pick Ironwood Branch and instantly click "Change Courier type".
7 .The wards will appear as a Book Rune just pick it using your hero
8. Voila! Free unlimited wards!</span><a name="more"></a>