Comment form fields pre filled with garbage

My comment fields have become pre-filled with garbage characters. As example, here is the HTML from my comment form on a page:

<p>
<label for="author">
<input name="author" id="author" value="nL7IYrTR7WHjWz0PhzUJJz5IHxqy_ZoqmyJV2q3fKpo." tabindex="1" class="TextField" style="width: 210px;" type="text">Name <small>(required)</small></label>
</p>

<p>
<label for="email">
<input name="email" id="email" value="0-Qdoa4Ya2dY1aPJ5oyh73qMo8OxOgbq_GC8DbYKiFx_6JAaC2gXw3GqzDbPTHeF" tabindex="2" class="TextField" style="width: 210px;" type="text">E-mail <small>(required, never displayed)</small></label>

</p>

<p>
<label for="url">
<input name="url" id="url" value="https://UgcuP3bdzS5Lt3Sm2IWTnnCtTw51ydTsEzO5KmKcwKdf_VxXlpd3QVhjWaHGrgMi" tabindex="3" class="TextField" style="width: 210px;" type="text"><abbr title="Uniform Resource Identifier">URI</abbr></label>
</p>

<p>
<textarea name="comment" id="comment" rows="10" tabindex="4" class="TextArea" style="width: 440px;"></textarea>
</p>

Any ideas?